Harley Davidson 2018 softail models. Service manual — page 34
1
ECU [266A]
2
Breakout box (BOB)
3
ECU harness [266B]
Figure 9. ABS Breakout Box Connection
HD-48650 Digital Technician II
DIGITAL TECHNICIAN II (Part Number:HD-48650) is a computer based diagnostic device used to
communicate/diagnose and program systems/modules.
Diagnostics in this manual are developed under the assumption that DTII is not available.
Voltage drop test:
Helps locate poor connections or components with excessive resistance.
Measures the difference in potential or actual voltage dropped between source and destination.
Checks integrity of the wiring, switches, fuses, connectors and contacts between source and destination.
Identifies poor grounds.
A voltage drop test measures the difference in voltage between two points in a circuit. The amount of voltage dropped over
any part of a circuit is directly related to the amount of resistance in that part of the circuit and the current flowing through
it.
Components such as wires, switches and connectors are designed to have very little resistance and very little voltage
drop. A voltage drop greater than 1.0V across these components indicates a high resistance and possible fault.
The benefits of testing this way are:
Readings are not as sensitive to real battery voltage.
Readings show the actual voltage dropped not just the presence of voltage.
System is tested as it is actually being used.
Testing is more accurate and displays hard-to-find poor connections.
Starting circuits, lighting circuits and ignition circuits can be tested with this approach. Start from the most positive and
go to the most negative destination or component.
When testing a typical power circuit, place positive (red) meter lead on most positive part of circuit or positive battery post.
There is nothing more positive than the positive post of the battery.
Place negative (black) meter lead at positive side of connector in question. Activate circuit. Move negative meter lead
through the circuit until high voltage drop is found.
When testing a typical ground circuit, place negative lead on most negative part of circuit or negative battery post. There is
nothing more negative than the negative post of the battery.
Place positive meter lead at negative side of connector in question. Activate circuit. Move positive meter lead through the
circuit until high voltage drop is found.
The following steps demonstrate a typical starter circuit voltage drop test:
1. Disconnect CKP [79] to prevent engine from starting.
a. See Figure 1. Set meter to VDC. Connect red meter lead to positive battery post.
b. Connect black meter lead to terminal 2 of starter solenoid. Observe meter reading.
c. Crank starter and observe meter reading. A reading higher than 1V indicates excessive voltage drop.
1
Terminal 1
2
Starter solenoid
3
Terminal 2
4
Starter motor
Figure 1. To Starter Solenoid Starter Terminal
2. See Figure 2. Move black meter lead to terminal 1 on starter solenoid. Crank starter. Observe voltage drop.
1
Terminal 1
2
Starter solenoid
3
Terminal 2
4
Starter motor
Figure 2. To Starter Solenoid Battery Terminal
3. See Figure 3. Move black meter lead to negative battery post and red meter lead to starter mounting bolt. Crank
starter. Observe voltage drop.
1
Terminal 1
2
Starter solenoid
3
Terminal 2
4
Starter motor
Figure 3. Starter Ground Circuit
Special Tools
Description
Part Number
Qty.
DIGITAL MULTIMETER (FLUKE 78)
HD-39978
1
DIGITAL TECHNICIAN II
HD-48650
1
BREAKOUT BOX
HD-50390-1
1
ECM CABLE
HD-50390-4
1
ECM OVERLAY
HD-50390-4-P
1
Wiggle test checks for the presence of intermittents in a wiring harness. If available, use DIGITAL TECHNICIAN II (Part
Number:HD-48650) to perform wiggle test.
1. See Figure 1. Connect DIGITAL MULTIMETER (FLUKE 78) (Part Number:HD-39978) to wiring harness between
suspect connections. When diagnosing ECM connections, use BREAKOUT BOX (Part Number:HD-50390-1),
ECM CABLE (Part Number:HD-50390-4) and ECM OVERLAY (Part Number:HD-50390-4-P) to simplify the
procedure. See How To Use Diagnostic Tools.
2. Set the multimeter to read voltage changes.
3. Start motorcycle engine and run at idle.
4. Shake or wiggle harness to detect intermittents. If intermittents are present, radical voltage changes register on
multimeter.
Figure 1. Digital Multimeter (Fluke 78)
Special Tools
Description
Part Number
Qty.
DIGITAL TECHNICIAN II
HD-48650
1
CAN bus circuits are used by modules and diagnostic tools to share information. The IM, ECM, BCM, hand controls and
ABS (if equipped) all communicate on the CAN bus. The CAN communication uses a (W/BK) and (W/R) wire in a twisted
pair that runs to all the modules. It is used to transfer data from one module to the other. It also runs to the DLC [91] and is
used to communicate with the modules using DIGITAL TECHNICIAN II (Part Number:HD-48650).
1
Battery tender [281]
2
DLC [91]
3
Termination resistor [319]
4
P&A accessory [325]
5
Fuse holder [332]
6
Fuse block [64]
7
ECM [78-3]
8
ECM [78-2]
9
ECM [78-1] (behind sub caddy)
Figure 1. Behind Left Side Cover
1
Engine harness [145]
2
ABS EHCU [166]
3
Rear HO2S [137]
4
Starter solenoid [128]
5
Rear WSS [168]
Figure 2. Behind Right Side Cover
1
Security siren [142]
2
BCM power [259]
3
BCM [242]
Figure 3. Front of Rear Tire
Special Tools
Description
Part Number
Qty.
DIGITAL TECHNICIAN II
HD-48650
1
Electronic Control Module (ECM)
See Behind Left Side Cover. The ECM is located under the left side cover. The ECM monitors the engine sensors to
enhance performance and driveability. This is done by adjusting the fuel and spark delivery based on the information
provided by the sensors.
IM
The IM contains part of the indicator and warning lamps for the motorcycle. It uses the CAN communication to receive
information from the other modules to know which lamps to illuminate at any given time. Vehicle speed is also sent to
the IM over the CAN bus. The LEDs in the indicator bar (if equipped) are directly wired to the IM. The IM turns the
indicators on and off based off commands from the other modules over the CAN bus.
BCM
See Behind Right Side Cover. The BCM is located on the electrical panel behind the fender extension. The BCM
supplies ignition and accessory power to most of the vehicle and controls the power mode of the electrical system. It
controls the lighting along with other functions on the vehicle by using the switches as inputs and the power circuits for
the lights as outputs. The BCM is also connected to the CAN bus and shares information with the other modules on
the vehicle.
ABS ECU
See Front of Rear Tire. The ABS ECU is located behind the right side panel. The ECU receives input from the front
and rear WSS, and controls the HCU accordingly. The ABS ECU communicates over the CAN bus to the IM to control
the ABS indicator.
Hand Control Modules
The left and right hand control modules control all the switches and controls on the handlebars. The engine stop switch
has a redundant wire directly to the BCM. In the event of a communication malfunction, this redundant circuit is used
to keep the engine from shutting off until the switch is turned off.
The hand controls also control the turn signals and running lights (DOM) on vehicles where the front turn signals are
wired to the hand controls.
Data Link Connector (DLC)
The DLC is located under the left side cover. The DLC is used to connect the DIGITAL TECHNICIAN II (Part
Number:HD-48650) to the motorcycle.
There are several DTCs that may set due to an issue with the CAN bus communication. Different DTCs are set by different
modules. If a module loses communication with the rest of the system it will set DTC U0001, but the DTC cannot be
retrieved until the CAN lines to that module are restored. If a module goes offline due to loss of PWR or GND or a loss of
communication to that module, the module will not set a code, but the other modules will set DTCs indicating they are not
able to communicate with it. When the IM recognizes a problem on the CAN bus it may display "BUS Err" on the
odometer.
"VINERR" may also be displayed in the odometer if the IM and ECM are not seeing the same VIN in both modules. This
will usually occur after replacing one of the two modules. The two modules must have the VINs match before they can
share odometer mileage.
Both the ECM and IM retain the odometer value. If the IM is replaced, it will display the odometer value stored in the ECM.
The replacement IM will become locked to the ECM after 50 km (31.1 mi) have been accumulated. The trip B odometer
will display the countdown mileage. Once the countdown reaches zero, the IM is locked to the ECM. If installed on another
vehicle, the odometer will display "VINERR". If the IM is removed from the vehicle before the countdown reaches zero, it
has not been locked to the ECM. This mileage countdown allows for a road test to verify that IM replacement was the
proper repair.
Diagnostic Tips
Modules must have power and be grounded in order to communicate. Therefore, when checking any communication
DTC be sure to check the power and ground connections on the suspected module. BUS Err may show on the
odometer if the following are present:
CAN wires shorted together.
CAN wire shorted to PWR or GND.
CAN transceiver on some module failed shorted.
Non-compliant module connected to the CAN bus.
Special Tools
Description
Part Number
Qty.
DIGITAL TECHNICIAN II
HD-48650
1
CAN communication uses a set of wires in a twisted pair. These two wires are designated as CAN low and CAN high
circuits. Both circuits are connected to the ECM, BCM, instruments, both hand control modules and the ABS ECU (if
equipped). The main harness and the right hand control module contain 120 ohm terminating resistors. Typical resistance
between the two circuits is approximately 60 ohms.
DTC U0001 indicates there is a fault on the CAN bus circuits. This code can be set by the ECM, BCM, instruments and
ABS ECU (if equipped). This code is usually accompanied by other "U" codes, due to it causing a loss of
communication between the modules on the CAN bus.
DTC U0011 indicates the high and low CAN circuits are shorted together. This fault will be accompanied by other "U"
codes and may cause the odometer display not to function.
DTC B2274 indicates there is a fault with the battery fuse or the (R/O) wire.
NOTE
Always start from Description and Operation before proceeding with this test.
Table 1. Code Description
DTC
DESCRIPTION
U0001
CAN bus error
U0011
CAN bus low shorted to CAN bus high
B2274
Constant battery line error
Diagnostic Tips
The IM does not have an ignition input. Instead, it receives a message over the CAN bus, indicating the IGN is ON.
Also, the trip odometer reset switch is a CAN communication to the IM. Therefore, CAN bus errors can cause the
odometer self-diagnostics to be completely inoperative or to only partially function. The IM backlighting may not
function along with the hand control switches and the indicators. The odometer may read "BUS Err" in this condition,
prior to the odometer becoming inoperative.
NOTE
If DIGITAL TECHNICIAN II (Part Number:HD-48650) is connected to the DLC [91] and communicating with the
vehicle, then the odometer self-diagnostics will not function properly. Disconnect DIGITAL TECHNICIAN II (Part
Number:HD-48650) before entering odometer self-diagnostics.
The BCM supplies power to several systems on the vehicle. When testing for a short to voltage, perform all tests
before disconnecting the BCM to keep from powering down systems on the vehicle. If the short to voltage goes away
when the BCM is disconnected, test for continuity between the circuit in question and BCM [242B] terminals F4, J3,
L3, L4 and M2 to verify the tested circuit is not shorted to one of these circuits. If continuity is present, repair short to
circuit instead of replacing the BCM.
Connector Information
For additional information about the connectors in the following diagram(s) and diagnostic procedure(s), see General.
Figure 1. CAN Bus Circuit
Special Tools
Description
Part Number
Qty.
TEST CONNECTOR KIT
HD-41404
1
BREAKOUT BOX
HD-42682
1
BREAKOUT BOX ADAPTERS
HD-46601
1
BREAKOUT BOX
HD-50390-1
1
BCM CABLE
HD-50390-2
1
BCM OVERLAY
HD-50390-2-P
1
ABS CABLE
HD-50390-6
1
Table 1. Odometer Self-Diagnostic Inoperative Diagnostic Faults: DTC U0001, U0011, B2274
POSSIBLE CAUSES
Short between CAN low and high circuits
Open in CAN high circuit
Open in CAN low circuit
Short to ground on CAN high circuit
Short to ground on CAN low circuit
Short to voltage on CAN high circuit
Short to voltage on CAN low circuit
1. CAN Bus Test
1. Turn IGN OFF.
2. Remove main fuse.
3. Using TEST CONNECTOR KIT (Part Number:HD-41404), test resistance between DLC [91A] terminals 1 and
3.
4. Is resistance between 50-70 ohms?
a. Yes. Go to Test 15.
b. No. Resistance less than 50 ohms. Go to Test 2.
c. No. Resistance greater than 70 ohms. Go to Test 10.
2. IM Test
1. Disconnect IM [39].
2. Is resistance between [91A] terminals 1 and 3 between 50-70 ohms?
a. Yes. Replace IM.
b. No. Go to Test 3.
3. BCM Test
1. Disconnect BCM [242].
2. Is resistance between [91A] terminals 1 and 3 between 50-70 ohms?
a. Yes. Replace BCM.
b. No, with ABS. Go to Test 4.
c. No, without ABS. Go to Test 5.
4. ABS Test
1. Disconnect ABS module [166].
2. Is resistance between [91A] terminals 1 and 3 between 50-70 ohms?
a. Yes. Replace ABS module.
b. No. Go to Test 5.
5. LHCM Test
1. Disconnect LHCM [24].
2. Is resistance between [91A] terminals 1 and 3 between 50-70 ohms?
a. Yes. Replace LHCM.
b. No, with tachometer. Go to Test 6.
c. No, without tachometer. Go to Test 7.
6. Tachometer Test
1. Disconnect tachometer [108].
2. Is resistance between [91A] terminals 1 and 3 between 50-70 ohms?
a. Yes. Replace tachometer.
b. No. Go to Test 7.
7. ECM Test
1. Disconnect ECM [78B-1].
2. Test resistance between [91A] terminals 1 and 3.
3. Is resistance between 50-70 ohms?
a. Yes. Replace ECM.
b. No. Go to Test 8.
8. Terminating Resistor Test
1. Disconnect terminating resistor [319].
2. Test resistance between [91A] terminals 1 and 3.
3. Is resistance between 110-130 ohms?
a. Yes. Replace terminating resistor.
b. No. Go to Test 9.
9. RHCM Test
1. Disconnect RHCM [22-1].
2. Test continuity between [91A] terminals 1 and 3.
3. Is continuity present?
a. Yes. Repair short between (W/R) and (W/BK) wires.
b. No. Replace RHCM.
10. CAN Circuit Open Test
1. Watch the resistance between DLC [91A] terminals 1 and 3, disconnect terminating resistor [319].
2. Did resistance change?
a. Yes. Go to Test 11.
b. No. Go to Test 13.
11. CAN High Circuit Resistance to RHCM Test
1. Disconnect RHCM [22-1].
2. Test resistance between [91A] terminal 1 (W/R) wire and [22A-1] terminal 3.
3. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/R) wire.
b. No. Go to Test 12.
12. CAN Low Circuit Resistance to RHCM Test
1. Test resistance between [91A] terminal 3 (W/BK) wire and [22A-1] terminal 4.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/BK) wire.
b. No. Replace RHCM.
13. CAN Low Circuit Resistance to Terminating Resistor Test
1. Test resistance between [91A] terminal 3 (W/BK) wire and [319B] terminal B.
NOTE
When measuring resistance (ohms), compensate for test lead resistance before performing the measurement.
Select the ohms position and touch the test leads together. Refer to the multimeter user's manual to either zero
the display or manually subtract the test lead resistance from the measured circuit's value.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/BK) wire.
b. No. Go to Test 14.
14. CAN High Circuit Resistance to Terminating Resistor Test
1. Test resistance between [91A] terminal 1 (W/R) wire and [319B] terminal A.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/R) wire.
b. No. Replace terminating resistor.
15. CAN High Circuit Short to Ground Test
1. Turn IGN OFF.
2. Test resistance between [91A] terminal 1 and ground.
3. Is resistance less than 1000 ohms?
a. Yes. Go to Test 16.
b. No. Go to Test 25.
16. IM Test
1. Disconnect IM [39].
2. Is resistance between [91A] terminal 1 and ground less than 1000 ohms?
a. Yes. Go to Test 17.
b. No. Replace IM.
17. ECM Test
1. Disconnect ECM [78B-1].
2. Is resistance between [91A] terminal 1 and ground less than 1000 ohms?
a. Yes. Go to Test 18.
b. No. Replace ECM.
18. Terminating Resistor Test
1. Disconnect terminating resistor [319].
2. Is resistance between [91A] terminal 1 and ground less than 1000 ohms?
a. Yes. Go to Test 19.
b. No. Replace terminating resistor.
19. LHCM Test
1. Disconnect LHCM [24].
2. Is resistance between [91A] terminal 1 and ground less than 1000 ohms?
a. Yes, with tachometer. Go to Test 20.
b. Yes, without tachometer. Go to Test 21.
c. No. Replace LHCM.
20. Tachometer Test
1. Disconnect tachometer [108].
2. Is resistance between [91A] terminals 1 and ground less than 1000 ohms?
a. Yes. Go to Test 21.
b. No. Replace tachometer.
21. BCM Test
1. Disconnect BCM [242].
2. Is resistance between [91A] terminal 1 and ground less than 1000 ohms?
a. Yes, with ABS. Go to Test 22.
b. Yes, without ABS. Go to Test 23.
c. No. Replace BCM.
22. ABS Test
1. Disconnect ABS module [166].
2. Is resistance between [91A] terminal 1 and ground less than 1000 ohms?
a. Yes. Go to Test 23.
b. No. Replace ABS module.
23. RHCM Test
1. Disconnect RHCM [22-1].
2. Is resistance between [91A] terminal 1 and ground less than 1000 ohms?
a. Yes. Repair short to ground in (W/R) wire.
b. No. Go to Test 24.
24. CAN Low Circuit Short to Ground Test
1. Test resistance between [91A] terminal 3 and ground.
2. Is resistance less than 1000 ohms?
a. Yes. Repair short to ground in (W/BK) wire.
b. No. Replace RHCM.
25. CAN High Circuit Short to Voltage Test
1. Install main fuse.
2. Turn IGN ON.
3. Test voltage between [91A] terminal 1 and ground.
4. Is voltage greater than 4V?
a. Yes. Go to Test 26.
b. No. Go to Test 34.
26. IM Test
1. Turn IGN OFF.
2. Disconnect IM [39].
3. Turn IGN ON.
4. Is voltage between [91A] terminal 1 and ground greater than 4V?
a. Yes. Go to Test 27.
b. No. Replace IM.
27. ECM Test
1. Turn IGN OFF.
2. Disconnect ECM [78B-1].
3. Turn IGN ON.
4. Is voltage between [91A] terminal 1 and ground greater than 4V?
a. Yes. Go to Test 28.
b. No. Replace ECM.
28. LHCM Test
1. Turn IGN OFF.
2. Disconnect LHCM [24].
3. Turn IGN ON.
4. Is voltage between [91A] terminal 1 and ground greater than 4V?
a. Yes, with ABS. Go to Test 29.
b. Yes, without ABS. Go to Test 30.
c. No. Replace LHCM.
29. ABS Test
1. Turn IGN OFF.
2. Disconnect ABS module [166].
3. Turn IGN ON.
4. Is voltage between [91A] terminal 1 and ground greater than 4V?
a. Yes. Go to Test 30.
b. No. Replace ABS module.
30. BCM Test
1. Turn IGN OFF.
2. Disconnect BCM power [259].
3. Disconnect BCM [242].
4. Turn IGN ON.
5. Is voltage between [91A] terminal 1 and ground greater than 4V?
a. Yes, with tachometer. Go to Test 31.
b. Yes, without tachometer. Go to Test 32.
c. No. Replace BCM. Refer to diagnostic tips.
31. Tachometer Test
1. Turn IGN OFF.
2. Disconnect tachometer [108].
3. Turn IGN ON.
4. Is voltage between [91A] terminals 1 and ground greater than 4V?
a. Yes. Go to Test 32.
b. No. Replace tachometer.
32. RHCM Test
1. Turn IGN OFF.
2. Disconnect RHCM [22-1].
3. Turn IGN ON.
4. Is voltage between [91A] terminal 1 and ground greater than 4V?
a. Yes. Repair short to voltage in (W/R) wire.
b. No. Go to Test 33.
33. CAN Low Circuit Short to Voltage Test
1. Test voltage between [91A] terminal 3 and ground.
2. Is voltage present?
a. Yes. Repair short to voltage in (W/BK) wire.
b. No. Replace RHCM.
34. CAN Low Circuit Resistance to BCM Test
1. Turn IGN OFF.
2. Disconnect BCM [242].
3. Connect BREAKOUT BOX (Part Number:HD-50390-1) and BCM CABLE (Part Number:HD-50390-2) to
wiring harness [242B], leaving [242A] disconnected.
4. Verify BCM OVERLAY (Part Number:HD-50390-2-P) is in position on BOB.
5. Test resistance between [91A] terminal 3 (W/BK) wire and BOB terminal E2.
6. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/BK) wire between [91A] terminal 3 and [242B] terminal E2.
b. No. Go to Test 35.
35. CAN High Circuit Resistance to BCM Test
1. Test resistance between [91A] terminal 1 (W/R) wire and BOB terminal D2.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/R) wire between [91A] terminal 1 and [242B] terminal D2.
b. No, with ABS. Go to Test 36.
c. No, without ABS. Go to Test 38.
d. No, without ABS or tachometer. Go to Test 40.
36. CAN Low Circuit Resistance to ABS Module Test
1. Remove cables and BCM BOB.
2. Connect BCM.
3. Disconnect ABS [166].
4. Connect BREAKOUT BOX (Part Number:HD-50390-1) and ABS CABLE (Part Number:HD-50390-6) to
wiring harness connector [166B]. Leaving [166A] disconnected, test resistance between [91A] terminal 3
(W/BK) wire and BOB terminal 11.
5. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/BK) wire between [91A] terminal 3 and [166B] terminal 11.
b. No. Go to Test 37.
37. CAN High Circuit Resistance to ABS Module Test
1. Test resistance between [91A] terminal 1 (W/R) wire and BOB terminal 2.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/R) wire between [91A] terminal 1 and [166B] terminal 2.
b. No, with tachometer Go to Test 38.
c. No, without tachometer. Go to Test 40.
38. CAN Low Circuit Resistance to Tachometer Test
1. Remove cables and ABS BOB. Connect ABS module.
2. Disconnect tachometer [108].
3. Connect BREAKOUT BOX (Part Number:HD-42682) and BREAKOUT BOX ADAPTERS (Part
Number:HD-46601) to wiring harness connectors [108B]. Leaving [108A] disconnected, test resistance
between [91A] terminal 3 (W/BK) wire and BOB terminal 8.
4. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/BK) wire between [91A] terminal 3 and [108B] terminal 8.
b. No. Go to Test 39.
39. CAN High Circuit Resistance to Tachometer Test
1. Test resistance between [91A] terminal 1 (W/R) wire and BOB terminal 2.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/R) wire between [91A] terminal 1 and [108B] terminal 2.
b. No. Go to Test 40.
40. IM Connector Test
1. Remove cables and ABS BOB, connect ABS module.
2. Remove tachometer BOB and connect tachometer.
3. Disconnect IM [39].
4. Inspect [39].
5. Is [39] a 12 place connector?
a. Yes. Go to Test 42.
b. No. Go to Test 41.
41. CAN Low Circuit IM Resistance Test
1. Using TEST CONNECTOR KIT (Part Number:HD-41404), test resistance between DLC [91A] terminal 3 and
IM [39B] terminal 5.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/BK) wire between [91A] terminal 3 and [39B] terminal 5.
b. No. Go to Test 44.
42. CAN Low Circuit Resistance to IM Test
1. Connect BREAKOUT BOX (Part Number:HD-42682) and BREAKOUT BOX ADAPTERS (Part
Number:HD-46601) to wiring harness connectors [39B].
2. Leaving [39A] disconnected, test resistance between [91A] terminal 3 (W/BK) wire and BOB terminal 8.
3. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/BK) wire between [91A] terminal 3 and [39B] terminal 8.
b. No. Go to Test 43.
43. CAN High Circuit Resistance to IM Test
1. Test resistance between [91A] terminal 1 (W/R) wire and BOB terminal 2.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/R) wire between [91A] terminal 1 and [39B] terminal 2.
b. No. Concern is intermittent. Perform wiggle test and verify all connectors are properly connected. See
Wiggle Test.
44. CAN High Circuit IM Resistance Test
1. Test resistance between [91A] terminal 1 (W/R) wire and IM [39] terminal 4.
2. Is resistance greater than 0.5 ohm?
a. Yes. Repair (W/R) wire between [91A] terminal 1 and [39B] terminal 4.
b. No. Concern is intermittent. Perform wiggle test and verify all connectors are properly connected. See
Wiggle Test.
Special Tools
Description
Part Number
Qty.
DIGITAL TECHNICIAN II
HD-48650
1
The CAN bus circuit provides a means for the ECM, IM, BCM, hand control modules and the ABS ECU (if equipped) to
communicate their current status. When all operating parameters on the CAN bus are within specifications, a state of
health message is sent between the components.
The CAN bus is made up of two circuits. The (W/R) is the CAN bus high circuit and the (W/BK) is the CAN bus low circuit.
Both of these circuits show approximately 2.5V when measured between each of the circuits and ground with the IGN ON.
These circuits are connected to each module on the CAN bus network. A fault on either one of these circuits will cause
several modules to set "U" codes and may cause a complete loss of communication between all modules.
Table 1. Code Description
DTC
DESCRIPTION
U0100
Lost comm w/ECM
U0121
Lost comm w/ABS
U0140
Lost comm w/BCM
U0141
Lost comm w/LHCM
U0142
Lost comm w/RHCM
U0156
Lost comm w/speedo
U0300
Internal control module software incompatibility
Diagnostic Tips
Modules must have power in order to communicate on the CAN bus. It is important to check for good power and
ground on any module that is not communicating effectively on the CAN bus network.
At least two modules will set a DTC when one module loses the ability to communicate on the CAN bus.
When two or more modules set the same U code it indicates a problem with the device or wiring at the device the
codes are set against.
Two or more modules setting the same U code intermittently indicates an intermittent problem with the device or
wiring.
See Wiggle Test to test wiring to the component.
The BCM supplies power to several systems on the vehicle.
When testing for a short to voltage, perform all tests before disconnecting the BCM to keep from powering down
systems on the vehicle.
If the short to voltage goes away when the BCM is disconnected, test for continuity between the circuit in question
and BCM [242B] terminals F4, J3, L3, L4 and M2 to verify the tested circuit is not shorted to one of these circuits.
If continuity is present, repair shorted circuit instead of replacing the BCM.
Historic U codes may be found if battery power has been lost for any reason or if the main or battery fuses have been
disconnected and reconnected. This may also happen during diagnostics using DIGITAL TECHNICIAN II (Part
Number:HD-48650). The diagnostics connector has been disconnected before vehicle has been powered down. This
is not an indication of a problem and does not cause any loss of functionality.
Connector Information
For additional information about the connectors in the following diagram(s) and diagnostic procedure(s), see General.
Figure 1. CAN Bus Circuit
Special Tools
Description
Part Number
Qty.
TEST CONNECTOR KIT
HD-41404
1
BREAKOUT BOX
HD-50390-1
1
ECM CABLE
HD-50390-4
1
ECM OVERLAY
HD-50390-4-P
1
Table 1. DTC U0100 Diagnostic Faults
POSSIBLE CAUSES
Open in CAN high circuit to the ECM
Open in CAN low circuit to the ECM
Open in ECM system power circuit
Open in ECM ground circuit
1. Module Test
1. View odometer.
2. Is only the BCM setting DTC?
a. Yes. Go to Test 10.
b. No, ABS ECU only. Go to Test 7.
c. No, IM only. Go to Test 8.
d. No, tachometer only. Go to Test 9.
e. No, multiple modules. Go to Test 2.
2. System Power Test
1. Turn IGN OFF.
2. Connect BREAKOUT BOX (Part Number:HD-50390-1) and ECM CABLE (Part Number:HD-50390-4) to
[78B-1], 78B-2] and [78B-3], leaving ECM [78A-1], [78A-2] and [78A-3] disconnected. See How To Use
Diagnostic Tools.
3. Verify ECM OVERLAY (Part Number:HD-50390-4-P) is in position on BOB.
4. Turn IGN ON.
5. Using TEST CONNECTOR KIT (Part Number:HD-41404), test voltage between BOB [78-2] terminal 16 and
ground.
6. Is battery voltage present?
a. Yes. Go to Test 3.
b. No. Go to Test 11.
3. ECM [78-1] Ground Test
1. Turn IGN OFF.
2. Test resistance between BOB [78-1] terminal 10 and ground.
3. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 4.
b. No. Repair open in (BK/GN) wire.
4. ECM [78-2] Ground Test
1. Test resistance between BOB [78-2] terminal 10 and ground.
2. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 5.
b. No. Repair open in (BK/GN) wire.
5. CAN High Circuit Continuity Test
1. Test resistance between BOB [78-1] terminal 14 and DLC [91A] terminal 1.
2. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 6.
b. No. Repair open in (W/R) wire.
6. CAN Low Circuit Continuity Test
1. Test resistance between BOB [78-1] terminal 13 and [91A] terminal 3.
2. Is resistance less than 0.5 ohm?
a. Yes. Replace ECM.
b. No. Repair open in (W/BK) wire.
7. Verify ABS ECU Test
1. Turn IGN OFF.
2. Replace ABS ECU with a known good ABS ECU.
3. Turn IGN ON.
4. Attempt to start vehicle.
5. Check DTC.
6. Is DTC U0100 present?
a. Yes. Check vehicle for any accessories connected to the CAN bus.
b. No. Replace ABS ECU.
8. Verify IM Test
1. Turn IGN OFF.
2. Replace IM with a known good IM.
3. Turn IGN ON.
4. Attempt to start vehicle.
5. Check DTC.
6. Is DTC U0100 present?
a. Yes. Check vehicle for any accessories connected to the CAN bus.
b. No. Replace IM.
9. Verify Tachometer Test
1. Turn IGN OFF.
2. Replace tachometer with a known good tachometer.
3. Turn IGN ON.
4. Attempt to start vehicle.
5. Check DTC.
6. Is DTC U0100 present?
a. Yes. Check vehicle for any accessories connected to the CAN bus.
b. No. Replace tachometer.
10. Verify BCM Test
1. Replace BCM with a known good BCM.
2. Turn IGN ON.
3. Attempt to start vehicle.
4. Check DTC.
5. Is DTC U0100 present?
a. Yes. Check vehicle for any accessories connected to the CAN bus.
b. No. Replace BCM.
11. System Power DTC Test
1. Remove BOB.
2. Connect [78A-1], [78A-2] and [78A-3].
3. Verify DTCs.
4. Is B2102, B2103 or B2104 setting?
a. Yes. See Description and Operation.
b. No. Repair open in (R/GN) wire.
Special Tools
Description
Part Number
Qty.
ABS BREAKOUT BOX
HD-48642
1
Table 1. DTC U0121 Diagnostic Faults
POSSIBLE CAUSES
Open in CAN high circuit to the ABS ECU
Open in CAN low circuit to the ABS ECU
Open in ABS system power circuit
Open in ABS ground circuit
1. ABS Voltage Test
1. Turn IGN OFF.
2. Connect ABS BREAKOUT BOX (Part Number:HD-48642) to wiring harness [166B], leaving [166A]
disconnected. See How To Use Diagnostic Tools.
3. Test voltage between BOB terminal 18 and ground.
4. Test voltage between BOB terminal 9 and ground.
5. Is battery voltage present at both?
a. Yes. Go to Test 2.
b. No. Repair open in (R) wire.
2. ABS Ground Test
1. Test voltage between BOB terminals 18 and 10.
2. Is battery voltage present?
a. Yes. Go to Test 3.
b. No. Repair open in (BK) wire.
3. CAN High Circuit Continuity Test
1. Turn IGN OFF.
2. Test resistance between BOB terminal 2 and DLC [91A] terminal 1.
3. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 4.
b. No. Repair open in (W/R) wire.
4. CAN Low Circuit Continuity Test
1. Test resistance between BOB terminal 11 and [91A] terminal 3.
2. Is resistance less than 0.5 ohm?
a. Yes. Replace ABS ECU.
b. No. Repair open in (W/BK) wire.
Special Tools
Description
Part Number
Qty.
TEST CONNECTOR KIT
HD-41404
1
BCM CABLE
HD-50390-2
1
BCM OVERLAY
HD-50390-2-P
1
Table 1. No Vehicle Power Diagnostic Faults: DTC U0140
POSSIBLE CAUSES
Open in CAN high circuit to the BCM
Open in CAN low circuit to the BCM
Open in ignition switch circuit
Short to ground in ignition switch circuit
Short to voltage in ignition switch circuit
Ignition switch malfunction
Open in BCM battery power circuit
Open in BCM ground circuit
1. BCM Ground Test
1. Turn IGN OFF.
2. Connect BCM OVERLAY (Part Number:HD-50390-2-P) and BCM CABLE (Part Number:HD-50390-2) to
wire harness [242B], leaving BCM [242A] disconnected.
3. Verify BCM OVERLAY (Part Number:HD-50390-2-P) is in position on BOB.
4. Disconnect BCM [259].
5. Using TEST CONNECTOR KIT (Part Number:HD-41404), test voltage between BCM [259B] terminal 1 and
BOB terminal G4.
6. Is battery voltage present?
a. Yes. Go to Test 2.
b. No. Go to Test 11.
2. CAN High Circuit Continuity Test
1. Disconnect RHCM [22A-1].
2. Test resistance between BOB terminal D2 and [22A-1] terminal 3.
3. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 3.
b. No. Repair open in (W/R) wire.
3. CAN High Circuit Short to Ground Test
1. Test continuity between BOB terminal D2 and ground.
2. Is continuity present?
a. Yes. Repair short to ground in (W/R) wire.
b. No. Go to Test 4.
4. CAN High Circuit Short to Voltage Test
1. Connect [259].
2. Connect [242A].
3. Turn IGN ON.
4. Test voltage between BOB terminal D2 and ground.
5. Is battery voltage present?
a. Yes. Repair short to voltage in (W/R) wire.
b. No. Go to Test 5.
5. CAN Low Circuit Continuity Test
1. Turn IGN OFF.
2. Test resistance between BOB terminal E2 and [22A-1] terminal 4.
3. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 6.
b. No. Repair open in (W/BK) wire.
6. CAN Low Circuit Short to Ground Test
1. Test continuity between BOB terminal E2 and ground.
2. Is continuity present?
a. Yes. Repair short to ground in (W/BK) wire.
b. No. Go to Test 7.
7. CAN Low Circuit Short to Voltage Test
1. Turn IGN ON.
2. Test voltage between BOB terminal E2 and ground.
3. Is battery voltage present?
a. Yes. Repair short to voltage in (W/BK) wire.
b. No. Go to Test 8.
8. RHCM Power Test
1. Test voltage between [22A-1] terminals 1 and 2.
2. Is battery voltage present?
a. Yes. Go to Test 10.
b. No. Go to Test 9.
9. RHCM Ground Test
1. Test voltage between [22A-1] terminal 1 and ground.
2. Is battery voltage present?
a. Yes. Repair open in (BK/GN) wire.
b. No. Repair open in (R/O) wire.
10. RHCM Test
1. Turn IGN OFF.
2. Remove main fuse [5].
3. Replace RHCM with a known good RHCM without installing it on the vehicle.
4. Install main fuse.
5. Push engine stop switch to RUN.
6. Turn IGN ON.
7. Does vehicle power up?
a. Yes. Replace RHCM.
b. No. Replace BCM.
11. BCM Voltage Test
1. Test voltage between [259B] terminal 1 and ground.
2. Is battery voltage present?
a. Yes. Repair open in (BK/GN) wire.
b. No. Repair open in (R) wire.
Special Tools
Description
Part Number
Qty.
TEST CONNECTOR KIT
HD-41404
1
Table 1. Left Hand Controls Inoperative, DTC U0141 Diagnostic Faults
POSSIBLE CAUSES
Open in CAN high circuit to the LHCM
Open in CAN low circuit to the LHCM
Open in LHCM battery power circuit
Open in LHCM ground circuit
1. LHCM Voltage Test
1. Turn IGN OFF.
2. Disconnect LHCM [24A].
3. Using TEST CONNECTOR KIT (Part Number:HD-41404), test voltage between [24A] terminal 1 and ground.
4. Is battery voltage present?
a. Yes. Go to Test 2.
b. No. Repair open in (R/O) wire.
2. LHCM Test
1. Test voltage between [24A] terminals 1 and 2.
2. Is battery voltage present?
a. Yes. Go to Test 3.
b. No. Repair open in (BK/GN) wire.
3. CAN High Circuit Continuity Test
1. Test resistance between [24A] terminal 3 and DLC [91A] terminal 1.
2. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 4.
b. No. Repair open in (W/R) wire.
4. CAN Low Circuit Continuity Test
1. Test resistance between [24A] terminal 4 and [91A] terminal 3.
2. Is resistance less than 0.5 ohm?
a. Yes. Replace LHCM.
b. No. Repair open in (W/BK) wire.
Special Tools
Description
Part Number
Qty.
TEST CONNECTOR KIT
HD-41404
1
Table 1. DTC U0142 Diagnostic Faults
POSSIBLE CAUSES
Open in CAN high circuit to the RHCM
Open in CAN low circuit to the RHCM
Open in RHCM battery power circuit
Open in RHCM ground circuit
1. RHCM Voltage Test
1. Turn IGN OFF.
2. Disconnect RHCM [22A-1].
3. Using TEST CONNECTOR KIT (Part Number:HD-41404), test voltage between [22A-1] terminal 1 and
ground.
4. Is battery voltage present?
a. Yes. Go to Test 2.
b. No. Repair open in (R/O) wire.
2. RHCM Test
1. Test voltage between [22A-1] terminals 1 and 2.
2. Is battery voltage present?
a. Yes. Go to Test 3.
b. No. Repair open in (BK/GN) wire.
3. CAN High Circuit Continuity Test
1. Test resistance between [22A-1] terminal 3 and DLC [91A] terminal 1.
2. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 4.
b. No. Repair open in (W/R) wire.
4. CAN Low Circuit Continuity Test
1. Test resistance between [22A-1] terminal 4 and [91A] terminal 3.
2. Is resistance less than 0.5 ohm?
a. Yes. Replace RHCM.
b. No. Repair open in (W/BK) wire.
Special Tools
Description
Part Number
Qty.
TEST CONNECTOR KIT
HD-41404
1
Table 1. IM Inoperative: DTC U0156 Diagnostic Faults
POSSIBLE CAUSES
Open in CAN high circuit to the IM
Open in CAN low circuit to the IM
Open in IM battery power circuit
Open in IM ground circuit
1. IM Voltage Test
1. Turn IGN OFF.
2. Using TEST CONNECTOR KIT (Part Number:HD-41404), test voltage between [20A] terminal 1 and ground.
3. Is battery voltage present?
a. Yes. Go to Test 2.
b. No. Repair open in (R/O) wire.
2. IM Ground Test
1. Test voltage between [20A] terminals 1 and 2.
2. Is battery voltage present?
a. Yes. Go to Test 3.
b. No. Repair open in (BK/GN) wire.
3. CAN High Circuit Continuity Test
1. Test resistance between [20A] terminal 3 and DLC [91A] terminal 1.
2. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 4.
b. No. Repair open in (W/R) wire.
4. CAN Low Circuit Continuity Test
1. Test resistance between [20A] terminal 4 and [91A] terminal 3.
2. Is resistance less than 0.5 ohm?
a. Yes. Replace IM.
b. No. Repair open in (W/BK) wire.
Special Tools
Description
Part Number
Qty.
TEST CONNECTOR KIT
HD-41404
1
BREAKOUT BOX
HD-42682
1
BREAKOUT BOX ADAPTERS
HD-46601
1
Table 1. Tachometer Inoperative: DTC U0157 Diagnostic Faults
POSSIBLE CAUSES
Open in CAN high circuit to the tachometer
Open in CAN low circuit to the tachometer
Open in tachometer battery power circuit
Open in tachometer ground circuit
1. Tachometer Voltage Test
1. Turn IGN OFF.
2. Connect BREAKOUT BOX (Part Number:HD-42682) and BREAKOUT BOX ADAPTERS (Part
Number:HD-46601) to the wiring harness [108B], leaving the [108A] disconnected.
3. Using TEST CONNECTOR KIT (Part Number:HD-41404), test voltage between BOB terminal 5 and ground.
4. Is battery voltage present?
a. Yes. Go to Test 2.
b. No. Repair open in (R/O) wire.
2. Tachometer Ground Test
1. Test voltage between BOB terminals 5 and 7.
2. Is battery voltage present?
a. Yes. Go to Test 3.
b. No. Repair open in (BK/GN) wire.
3. CAN High Circuit Continuity Test
1. Test resistance between BOB terminal 2 and DLC [91A] terminal 1.
2. Is resistance less than 0.5 ohm?
a. Yes. Go to Test 4.
b. No. Repair open in (W/R) wire.
4. CAN Low Circuit Continuity Test
1. Test resistance between BOB terminal 8 and [91A] terminal 3.
2. Is resistance less than 0.5 ohm?
a. Yes. Replace the tachometer.
b. No. Repair open in (W/BK) wire.
Special Tools
Description
Part Number
Qty.
DIGITAL TECHNICIAN II
HD-48650
1
Table 1. DTC U0300 Diagnostic Faults
POSSIBLE CAUSES
ECM software error
1. Verify DTC
1. Clear DTC.
2. Turn IGN OFF for 30 seconds.
3. Check DTCs.
4. Did DTC reset?
a. Yes. Go to Test 2.
b. No. System working properly.
2. Reflash ECM
1. Using DIGITAL TECHNICIAN II (Part Number:HD-48650) reflash ECM.
2. Clear DTCs.
3. Turn IGN OFF for 30 seconds.
4. Check DTCs.
5. Did DTC reset?
a. Yes. Replace ECM.
b. No. System working properly.
Test battery condition by using a voltage, charging or load test.
Always fully charge battery prior to load testing.
NOTE
An automatic, constant monitoring battery charger/tender with a charging rate of 5 amps or less at less than 14.6V is
recommended. The use of constant current chargers (including trickle chargers) to charge sealed AGM batteries is not
recommended. Any overcharge will cause dry-out and premature battery failure.
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