Page 1438 of 5267
6.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace and program the Powertrain Control Module per Service Information.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1440 of 5267

When Monitored:
With the ignition key on and the engine speed greater than 0 RPM.
Set Condition:
When the PCM regulates the generator field and there are no detected field problems, but the voltage output
does not decrease.
Possible Causes
(K20) GENERATOR FIELD CONTROL CIRCUIT SHORTED TO GROUND
GENERATOR FIELD COIL SHORTED TO GROUND
BATTERY TEMPERATURE SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.CHARGING SYSTEM OPERATION
NOTE: Battery must be fully charged and be capable of passing a load test.
NOTE: Generator Belt tension and condition must be checked before continuing.
Ignition on, engine not running.
With the scan tool, read DTCs and the related Freeze Frame data then clear theDTCs.
With scan tool, actuate the Generator Field Driver.
With a 12-volt test light connected to ground, backprobe the (K20) Gen Field Control circuit in the back of Generator
Field harness connector.
Does the test light illuminate brightly and flash?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.(K20) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the C2 PCM harness connector.
Disconnect the Generator Field Harness connector.
Carefully inspect the related connectors for corrosion or spread termi-
nals before continuing.
Measure the resistance between ground and the (K20) Generator Field
Driver circuit at the Generator Field harness connector.
Istheresistancebelow100ohms?
Ye s>>
Repair the short to ground in the (K20) Generator Field
Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
Page 1441 of 5267

3.GENERATOR FIELD COIL SHORTED TO GROUND
Measure the resistance between ground and the Generator Field terminals on the Generator.
Istheresistancebelow100ohms?
Ye s>>
Replace or repair the Generator Field Coil for a short to ground.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.BATTERY TEMPERATURE SENSOR
Connect the PCM harness connectors and the Generator harness connector.
Ignition on, engine not running.
With the scan tool in Inputs/Outputs, read the Batt Temp Sensor value.
Using a thermometer measure under hood temperature near Battery tray.
Is the temperature within 10 deg of Battery temperature?
Ye s>>
Go To 5
No>>
Replace the Battery Temperature Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1445 of 5267

5.(C918) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO THE (F855) 5-VOLT SUPPLY CIRCUIT
Measure the resistance between the (C918) A/C Pressure Signal circuit
and the (F855) 5-volt Supply circuit in the A/C Pressure Sensor harness
connector.
Is the resistance below 5.0 ohms?
Ye s>>
Repair the short between the (F855) 5-volt Supply circuit
and the (C918) A/C Pressure Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 6
6.(K900) SENSOR GROUND CIRCUIT OPEN
Measure the resistance of the (K900) Sensor ground circuit from the
A/C Pressure Sensor harness connector to the PCM harness connector.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 7
No>>
Repair the open in the (K900) Sensor ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
7.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1449 of 5267

6.(F855) 5-VOLT SUPPLY CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connectors.
Measure the resistance of the (F855) 5-volt Supply circuit between the
A/C Pressure Transducer harness connector and the PCM harness con-
nector.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 7
No>>
Repair the open in the (F855) 5-volt Supply circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
7.(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
Measure the resistance between the (F855) 5-volt Supply circuit and
ground in the A/C Pressure Transducer harness connector.
Istheresistancebelow100ohms?
Ye s>>
Repair the short to ground in the (F855) 5-volt Supply cir-
cuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 8
8.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1451 of 5267

When Monitored:
With the ignition key on and the engine running over 1500 RPM after 25 seconds.
Set Condition:
When the PCM regulates the generator field and there are no detected field problems, but the voltage output
does not increase.
Possible Causes
BATTERY TEMPERATURE SENSOR
RESISTANCE IN THE BATTERY POSITIVE CIRCUIT
(K125) GENERATOR FIELD SOURCE CIRCUIT OPEN
RESISTANCE IN THE GENERATOR GROUND
(K125) GENERATOR FIELD SOURCE CIRCUIT SHORTED TO GROUND
(K20) GENERATOR FIELD CONTROL CIRCUIT OPEN
RESISTANCE IN THE GENERATOR FIELD COIL
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.CHARGING VOLTAGE BELOW 15.1 VOLTS
Turn the ignition off.
NOTE: Battery must be fully charged and capable of passing a battery load test.
NOTE: Generator Belt tension and condition must be checked before continuing.
NOTE: Inspect the vehicle for any aftermarket accessories that may exceedthe maximum Generator output.
WARNING: When the engine is operating, do not stand in direct line of the fan. Do not put your hands near
the pulley, belts, or fan. Do no wear loose clothing.
Start the engine.
Record all DTCs and the related Freeze Frame data.
With the scan tool, read the target charging voltage.
Is the target charging voltage above 15.1 volts?
Ye s>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 2
2.BATTERY TEMPERATURE SENSOR
Turn the ignition off.
NOTE: Generator Belt tension and condition must be checked before continuing.
Start the engine.
Allow the engine to reach normal operating temperature.
With the scan tool in sensors, read the Battery Temp Sensor value.
Using a Thermometer, measure under hood temperature.
Is the temperature within 10° F of Battery temperature?
Ye s>>
Go To 3
No>>
Replace the Battery Temperature Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1454 of 5267
9.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1459 of 5267
3.(D25) PCI BUS CIRCUIT OPEN
Turn the ignition off.
Disconnect the C3 PCM harness connector.
Disconnect the FCM harness connector.
NOTE: Inspect the PCI Bus terminal at both the PCM connectors
and the FCM connectors. Check for corrosion, damage or terminal
push out.
Measure the resistance of the (D25) PCI BUS circuit between the C3
PCM harness connector and the FCM harness connector.
Is the resistance below 5.0 ohms?
Ye s>>
Replace and program the Powertrain Control Module per
Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Repair the open in the (D25) PCI BUS circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)