Isuzu engine C22NE / 22LE / 20LE. Manual — part 97
DRIVEABILITY AND EMISSIONS 6E1-217
A/C
Compressor
Relay
Control
A16
MAG
Clutch
(Compressor)
Relay
Thermo
(1)
(2)
(3)
(4)
Relay:A/C
Compressor
Joint
To HA09
0.5
BR
0.5
GR/R
B10
0.5
G/B
HOT IN START AND RUN
(2)
(1)
(4)
(3)
Engine
Control
Module
(ECM)
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 87)
A/C COMPRESSOR CLUTCH RELAY LOW 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 87
will set.
Conditions for Setting the DTC
• Driver feedback information shows a low state at its
operation even when commanded high.
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
ground or open contact 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.
6E1-218 DRIVEABILITY AND EMISSIONS
• Damaged harness-Inspect the wiring harness for
damage; shorts to Ground, 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 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 = 87)
A/C Compressor Clutch Relay Low 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 87.
Does the Scan Tool indicate DTC 87?
-
Refer to
Diagnostic Aids
Go to Step 3
3
1. Ignition OFF.
2. Check for an open circuit at the pressure switch and
thermo switch.
And also check for an open circuit at the wire harness
between pressure switch and the ECM, pressure
switch and thermo switch, thermo switch and the Fuse.
Repair it necessary.
-
Verify Repair
Go to Step 4
4
1. Remove the A/C Compressor Clutch Relay from the
Underhood Electrical Center.
2. Ignition ON, engine OFF.
3. 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 6
Go to Step 5
5
Check the suspect circuit(s) between the A/C Compressor
Clutch Relay connector and the Fuse for the following
conditions:
• A short to ground
• An open circuit
Was the problem found?
-
Verify Repair
-
6
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 ground
• An open circuit
Was the problem found?
-
Verify Repair
Go to Step 7
DRIVEABILITY AND EMISSIONS 6E1-219
DTC (Flash DTC = 87)
A/C Compressor Clutch Relay Low Error (Cont'd)
Step
Action
Value(s)
Yes
No
7
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 10
Go to Step 8
8
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 ground
• An open circuit
Was the problem found?
-
Verify Repair
Go to Step 9
9
Replace the A/C Compressor Clutch Relay.
Is the action complete?
-
Verify Repair
-
10
Replace the EPROM or ECM.
Varify Repair
Note) Refer to 6E1-243.
-
-
-
6E1-220 DRIVEABILITY AND EMISSIONS
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