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 1442 of 5267
P1598-A/C PRESSURE SENSOR VOLTAGE TOO HIGH
For a complete wiring diagramRefer to Section 8W.
Page 1443 of 5267

When Monitored:
With the engine running and the A/C Relay energized.
Set Condition:
The A/C Pressure Sensor Signal at the PCM goes above 4.92 volts.
Possible Causes
(C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO VOLTAGE
(C18) A/C PRESSURE SIGNAL CIRCUIT OPEN
(C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO THE (F855) 5-VOLT SUPPLY CIRCUIT
(K900) SENSOR GROUND CIRCUIT OPEN
A/C PRESSURE SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.A/C PRESSURE SENSOR VOLTAGE ABOVE 4.9 VOLTS
NOTE: Make sure the A/C refrigerant System is properly charged per the Service Information.
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
Start the engine.
With the scan tool, read the A/C Pressure Sensor voltage.
Is the voltage above 4.9 volts?
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.A/C PRESSURE SENSOR
Turn the ignition off.
Disconnect the A/C Pressure Sensor harness connector.
Connect a jumper wire between the (C918) A/C Pressure Signal circuit
and the (K900) Sensor ground circuit in the Sensor harness connector.
With the scan tool, monitor the A/C Pressure Sensor voltage.
Ignition on, engine not running.
Is the voltage below 1.0 volt?
Ye s>>
Replace the A/C Pressure Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
NOTE: Remove the jumper wire before continuing.
Page 1444 of 5267
3.(C918) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the PCM harness connectors.
Ignition on, engine not running.
Measure the voltage on the (C918) A/C Pressure Signal circuit in the
A/C Pressure Sensor harness connector.
Is the voltage above 5.2 volts?
Ye s>>
Repair the short to voltage in the (C918) A/C Pressure Sig-
nal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.(C918) A/C PRESSURE SIGNAL CIRCUIT OPEN
Turn the ignition off.
Measure the resistance of the (C918) A/C Pressure Signal circuit
between the A/C Pressure Sensor harness connector and the PCM har-
ness connector.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 5
No>>
Repair the open in the (C918) A/C Pressure Signal circuit.
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 1446 of 5267
P1599-A/C PRESSURE SENSOR VOLTAGE TOO LOW
For a complete wiring diagramRefer to Section 8W.
Page 1447 of 5267

When Monitored:
With the engine running and the A/C Relay energized.
Set Condition:
The A/C Pressure Transducer Signal voltage at the PCM goes below 0.58 voltsfor 2.6 seconds.
Possible Causes
(F855) 5-VOLT SUPPLY CIRCUIT OPEN
(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
A/C PRESSURE SENSOR
(C918) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO GROUND
(C918) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.A/C PRESSURE SENSORr VOLTAGE BELOW 0.6 VOLTS
NOTE: Make sure the A/C refrigerant System is properly charged per the Service Information.
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
Start the engine.
With the scan tool, read the A/C Pressure Transducer voltage.
Is the voltage below 0.60 of a volt?
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.(F855) 5-VOLT SUPPLY CIRCUIT
Turn the ignition off.
Disconnect the A/C Pressure Transducer harness connector.
Ignition on, engine not running.
Measure the voltage on the (F855) 5-volt Supply circuit in the A/C Pres-
sure Transducer harness connector.
Is the voltage between 4.5 to 5.2 volts?
Ye s>>
Go To 3
No>>
Go To 6
Page 1448 of 5267

3.A/C PRESSURE TRANSDUCER
With the scan tool, monitor the A/C Pressure Transducer voltage with the Transducer disconnected.
Is the voltage above 0.6 of a volt?
Ye s>>
Replace the A/C Pressure Transducer.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.(C918) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the PCM harness connectors.
Measure the resistance between ground and the (C918) A/C Pressure
Signal circuit in the A/C Pressure Transducer harness connector.
Istheresistancebelow100ohms?
Ye s>>
Repair the short to ground in the (C918) A/C Pressure Sig-
nal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 5
5.(C918) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
Measure the resistance between the (C918) A/C Pressure Signal circuit
and the (K900) Sensor ground circuit in the A/C Pressure Transducer
harness connector.
Istheresistancebelow100ohms?
Ye s>>
Repair the short between the (K900) Sensor ground and the
(C918) A/C Pressure Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 8