Isuzu engine C22NE / 22LE / 20LE. Service manual — part 85
DRIVEABILITY AND EMISSIONS 6E1-169
Engine
Control
Module
(ECM)
CKP
Sensor
Input
Sensor
Ground
0.5
G
E5
0.5
R
F1
Crankshaft
Position
(CKP)
Sensor
2
1
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 19)
CRANKSHAFT POSITION (CKP) SENSOR SIGNAL INCORRECT
Circuit Description
The 58X reference signal is produced by the
crankshaft position (CKP) sensor. During one
crankshaft revolution, 58 crankshaft pulses will be
produced. The engine control module (ECM) uses the
58X reference signal to calculate engine RPM and
crankshaft position. The ECM constantly monitors the
number of pulses on the 58X reference circuit. If the
ECM receives an incorrect number of pulses on the
58X reference circuit, Diagnostic Trouble Code 19 will
set.
Conditions for Setting the DTC
• Engine is running.
• Number of revolutions with pulses not equal to 58 is
greater than 20.
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL) after the fault is detected.
Conditions for Clearing the MIL/DTC
Once the ECM determines that a fault(s) has been
rectified then the CEL will switch OFF, although the
fault code will remain in the ECM memory.
Any fault codes will remain in ECM memory until -
1. They are cleared by disconnecting the Battery for
more than 30 seconds.
2. A service tool such as Tech 2 is used to clear them.
3. Ten consecutive starts without logging a fault.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed-through wire insulation or a wire broken inside
the insulation. Check for:
• Poor connection - Inspect the ECM harness and
connectors for improper mating, broken locks,
improperly formed or damaged terminals, and poor
terminal-to-wire connection.
6E1-170 DRIVEABILITY AND EMISSIONS
• Damaged harness - Inspect the wiring harness for
damage; shorts to Ground, shorts to Battery
Positive, and Open circuits. If the harness appears
to be OK, disconnect the ECM, turn the ignition on
and observe a voltmeter connected to the 58X
reference circuit at the ECM harness connector
while moving connectors and wiring harnesses
related to the ECM. A change in voltage will indicate
the location of the fault.
• This code detects an incorrect 58X signal caused
by intermittent failures.
DTC (Flash DTC = 19)
Crankshaft Position (CKP) Sensor Signal Incorrect
Step
Action
Value(s)
Yes
No
1
Was the "On-Board Diagnostic (OBD) System Check"
performed?
-
Go to Step 2
Go to OBD
System
Check
2
Attempt to start the engine.
Does the engine start?
-
Go to Step 3
Refer to
Engine
Cranks But
Will Not Run
chart
3
1. Clear Diagnostic Trouble Code 19.
2. Start the engine and idle for 1 minute.
3. Observe Diagnostic Trouble Codes.
Is Diagnostic Trouble Code 18 set?
-
Go to Step 4
Refer to
Diagnostic
Aids
4
1. Disconnect the ECM and CKP sensor.
2. Check for an open or a short to ground in the 58X
reference circuit between the CKP sensor connector
and the ECM harness connector.
3. If a problem is found, repair as necessary.
Was a problem found?
-
Verify repair
Go to Step 5
5
1. Reconnect the ECM and CKP sensor.
2. Connect a Digital Voltmeter (DVM) to measure voltage
on the 58X reference circuit at the ECM connector.
3. Observe the voltage while cranking the engine.
Is the voltage near the specified value?
2.5V
Go to Step 8
Go to Step 6
6
Check the connections at the CKP sensor and replace the
terminals if necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 7
7
Replace the CKP sensor.
Is the action complete?
-
Verify repair
-
8
Check connections at the ECM and replace the terminals
if necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 9
9
Replace the EPROM or ECM.
Is the action complete?
Note) Refer to 6E1-243.
-
Verify repair
-
DRIVEABILITY AND EMISSIONS 6E1-171
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 24)
VEHICLE SPEED SENSOR (VSS) FAULT
Circuit Description
The vehicle speed sensor has a magnet rotated by the
transmission output shaft. Attached to the sensor is a
hall effect circuit that interacts with the magnetic field
created by the rotating magnet. A 12-volt operating
supply for the speed sensor hall circuit is supplied
from the meter fuse. The VSS pulses to ground the 5-
volt signal sent from the engine control module (ECM)
on the reference circuit. The ECM interprets vehicle
speed by the number of pulses to ground per second
on the reference circuit. Then a DTC 24 will set.
Conditions for Setting the DTC
• Vehicle speed is less than 3 km/h.
• Engine is running.
• MAP is less than 24kPa.
• Throttle closed and in Drive.
• Engine Speed is between 2000 RPM and 5000
RPM.
• Following malfunctions are not set: DTC 21, 22, 33,
34 are not set.
When the above conditions are met, one of the
following tests will run:
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL) the fault is detected.
Conditions for Clearing the MIL/DTC
Once the ECM determines that a fault(s) has been
rectified then the CEL will switch OFF, although the
fault code will remain in the ECM memory.
Any fault codes will remain in ECM memory until -
1. They are cleared by disconnecting the Battery for
more than 30 seconds.
2. A service tool such as Tech 2 is used to clear them.
3. Ten consecutive starts without logging a fault.
6E1-172 DRIVEABILITY AND EMISSIONS
Diagnostic Aids
• Poor connection at the ECM: Inspect harness
connectors for backed out terminals, improper
mating, broken locks, improperly formed or
damaged terminals, and poor terminal to wire
connection.
• Damaged harness: Inspect the wiring harness to
the Speedometer, Tachometer and check Engine
Lamp for an intermittent open or intermittent short
circuit.
DTC (Flash DTC = 24)
Vehicle Speed Sensor (VSS) Fault
Step
Action
Value(s)
Yes
No
1
Was the "On-Board Diagnostic (OBD) System Check"
performed?
-
Go to Step 2
Go to OBD
System Check
2
1. Ignition OFF.
2. Disconnect the VSS connector.
3. Using a test light to battery
+, probe the connector
ground wire.
Did the light illuminate?
-
Go to Step 4
Go to Step 3
3
Repair the open in the sensor ground circuit.
-
Verify repair
-
4
1. Ignition ON.
2. Using a Digital Voltmeter (DVM), measure at the VSS
connector between ground and voltage supply.
Was the measurement near the specified value?
Battery
voltage
Go to Step 6
Go to Step 5
5
Repair the open or short to ground in the sensor circuit.
-
Verify repair
-
6
1. Ignition OFF.
2. Check the white wire between the VSS sensor
connector and the ECM for the following conditions:
• An open circuit
• A short to ground
Was the faulty condition located?
-
Verify repair
Go to Step 9
7
Using a DVM, measure the resistance between the VSS
sensor body and transmission case (ground).
Is the resistance above the specified value?
10K
OHMS
Verify repair
Go to Step 9
8
1. Remove the VSS from the transmission case.
2. Visually inspect the VSS for damage.
Does the VSS appear to be OK?
-
Verify repair
-
9
Replace the VSS
-
Verify repair
-
10
Replace the EPROM or ECM.
Verify repair.
Note) Refer to 6E1-243.
-
Verify repair
-
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