For a complete wiring diagram Refer to Section 8W.When Monitored:Engine running and the A/C Clutch Relay energized.Set Condition:The A/C pressure transducer signal at the PCM goes above 4.92 volts. One trip Fault. Three good trips to turn off the MIL.Possible Causes(C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE(C18) A/C PRESSURE SIGNAL CIRCUIT OPEN(C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO THE (C818) 5-VOLT SUPPLY CIRCUIT(C918) A/C PRESSURE GROUND CIRCUIT OPENA/C PRESSURE TRANSDUCERPCMAlways perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).1. A/C PRESSURE TRANSDUCER VOLTAGE ABOVE 4.9 VOLTSDiagnose any CAN - C Communication DTCs before continuing.Make sure the A/C refrigerant system is properly charged per Service Information.Start the engine.With a scan tool, read the A/C Pressure Sensor voltage.Is the voltage above 4.9 volts?YesGo To 2NoRefer to the INTERMITTENT CONDITION Diagnostic Procedure.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)2. A/C PRESSURE TRANSDUCER

Turn the ignition off.Disconnect the A/C Pressure Transducer harness connector.Connect a jumper wire between the (C18) A/C Pressure Signal circuit and the (C918) Sensor Ground circuit in the Transducer harness connector.Ignition on, engine not running.With the scan tool, monitor the A/C Pressure Transducer voltage.Is the voltage below 1.0 volt with the jumper wire installed?YesReplace the A/C Pressure Transducer.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 3Remove the jumper wire before continuing.3. (C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

Turn the ignition off.Disconnect the C1 TIPM harness connector.Ignition on, engine not running.Measure the voltage on the (C18) A/C Pressure Signal circuit in the A/C Pressure Transducer harness connector.Is the voltage above 0 volts?YesRepair the short to battery voltage in the (C18) A/C Pressure Signal circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 44. (C18) A/C PRESSURE SIGNAL CIRCUIT OPEN

Turn the ignition off.Measure the resistance of the (C18) A/C Pressure Signal circuit from the A/C Pressure Transducer harness connector to C1 TIPM harness connector.Is the resistance below 5.0 ohms?YesGo To 5NoRepair the open in the (C18) A/C Pressure Signal circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)5. (C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO THE (C818) 5-VOLT SUPPLY CIRCUIT

Measure the resistance between the (C18) A/C Pressure Signal circuit and the (C818) 5-volt Supply circuit in the A/C Pressure Transducer harness connector.Is the resistance below 5.0 ohms?YesRepair the short between the (C818) 5-volt Supply circuit and the (C18) A/C Pressure Signal circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 66. (C918) SENSOR GROUND CIRCUIT OPEN

Measure the resistance of the (C918) Sensor Ground circuit from the A/C Pressure Sensor harness connector to the C1 TIPM harness connector.Is the resistance below 5.0 ohms?YesGo To 7NoRepair the open in the (C918) Sensor Ground circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)7. TOTALLY INTEGRATED POWER MODULEBefore continuing, check the TIPM 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.Were any problems found?YesRepair as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoReplace the Totally Integrated Power Module per Service Information.Perform the BODY VERIFICATION TEST – VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE)