Isuzu engine C22NE / 22LE / 20LE. Manual — part 98
DRIVEABILITY AND EMISSIONS 6E1-221
Engine
Control
Module
(ECM)
A/C
Compressor
Relay
Control
A16
B10
Thermo
Switch
Pressure
Switch
0.5G/W
0.5G/W
0.5G/W
A/C Switch
0.5
G/Y
0.5
GR/Y
0.5
G/R
0.5
G/B
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 88)
A/C COMPRESSOR CLUTCH RELAY HIGH ERROR
Circuit Description
The engine control module (ECM) controls the A/C
Compressor Clutch Solenoid through the use of a
relay and a control (ground) circuit. This malfunction
detects a low impedance short to ground or open
contact on the A/C clutch relay output, then DTC 88
will set.
Conditions for Setting the DTC
• Driver feedback information shows a high state at
its operation even when commanded low.
Action Taken When the DTC Sets
• The ECM will illuminate Malfunction Indicator lamp
(MIL).
Conditions for Clearing the 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
• This malfunction detects a low impedance short to
battery on the AC clutch relay output.
To diagnose an intermittent fault, check for the
following conditions:
• Poor connection at the ECM-Inspect harness
connections 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 for
damage; shorts to Battery Voltage, and Open
circuits. If the harness appears to be OK, observe
the A/C clutch while moving connectors and wiring
harnesses related to the A/C. A sudden clutch
6E1-222 DRIVEABILITY AND EMISSIONS
malfunction will indicate the source of the
intermittent fault.
A/C Clutch Diagnosis
This chart should be used for diagnosing the electrical
portion of the A/C compressor clutch circuit. A Scan
Tool will be used in diagnosing the system. The Scan
Tool has the ability to read the A/C request input to the
ECM. The Scan Tool can display when the ECM has
commanded the A/C clutch ON. The Scan Tool should
have the ability to override the A/C request signal and
energize the A/C compressor relay.
DTC (Flash DTC = 88)
A/C Compressor Clutch Relay High Error
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 ON, engine OFF.
2. Using the Scan Tool, monitor info for DTC 88.
Does the Scan Tool indicate DTC 88?
-
Refer to
Diagnostic Aids
Go to Step 3
3
1. Ignition OFF.
2. Remove the A/C Compressor Clutch Relay from the
Underhood Electrical Center.
3. Ignition ON, engine OFF.
4. Using a Digital Voltmeter (DVM), check for voltage on
the Fused pins of the A/C Compressor Clutch Relay
connector.
Does the DVM read the following value?
12 Volts
Go to Step 4
Go to Step 5
4
1. Ignition OFF.
2. Disconnect the Engine Control Module (ECM)
connectors from the ECM.
3. Check the A/C Compressor Clutch Relay control circuit
between the ECM and Underhood Electrical Center for
the following conditions:
• A short to battery
Was the problem found?
-
Verify Repair
Go to Step 5
5
1. Reinstall the A/C Compressor Clutch Relay.
2. Using a fused jumper, ground the A/C Compressor
Clutch Relay control circuit at the ECM connector.
3. Ignition ON, Engine OFF.
Does the A/C Compressor turn ON?
-
Go to Step 8
Go to Step 6
6
1. Ignition OFF.
2. Check the A/C Compressor Clutch circuit between the
A/C Compressor Clutch Relay and A/C Compressor
Clutch for the following conditions:
• A short to battery
Was the problem found?
-
Verify Repair
Go to Step 7
7
Replace the A/C Compressor Clutch Relay.
Is the action complete?
-
Verify Repair
-
8
Replace the EPROM or ECM.
Varify Repair
Note) Refer to 6E1-243.
-
-
-
DRIVEABILITY AND EMISSIONS 6E1-223
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 93)
QUAD DRIVER SUB MODULE
Circuit Description
Quad Driver Sub Module (QDSM) are used by the
engine control module (ECM) to turn ON many of the
current-driven devices that are needed to control
various engine and transmission functions. Each
QDSM is capable of controlling up to 4 separate
outputs by applying ground to the device which the
ECM is commanding ON.
QDSMs have the capability of diagnosing each output
circuit individually. DTC 93 set indicates an improper
voltage level has been detected on a QDSM output.
This DTC detects a short to battery or Open Load or
Short to ground at the QDSM output, then DTC P93
will set.
Conditions for Setting the DTC
• If fault line from the QDSM is detected low.
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL).
Conditions for Clearing the 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
Check for the following conditions:
• Poor connection at 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 for
damage. If the harness appears to be OK,
disconnect the ECM, turn the ignition ON and
6E1-224 DRIVEABILITY AND EMISSIONS
observe a voltmeter connected to the MIL driver
circuit at the ECM harness connector while moving
connectors and rewiring harnesses relates to the
MIL. A change in voltage will indicate the location of
the fault.
This malfunction detects a:
Short to battery or Open Load or Short to ground at
QDSM output.
DTC (Flash DTC = 93)
Quad Driver Sub Module
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
Replace the EPROM or ECM.
Note) Refer to 6E1-243.
Is the action complete?
-
Verify Repair
-
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