Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

1) A/C PRESSURE TRANSDUCER VOLTAGE ABOVE 4.9 VOLTS
NOTE: 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?

Yes
1. Go To step 2).
No
1. Refer to INTERMITTENT CONDITION .
2. Perform POWERTRAIN VERIFICATION TEST .
2) A/C PRESSURE TRANSDUCER

Fig 1: Checking A/C Pressure Sensor
Courtesy of DAIMLERCHRYSLER CORP.

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 Return 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?

Yes
1. Replace the A/C Pressure Transducer.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 3).
  NOTE: Remove the jumper wire before continuing.
3) (C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

Fig 2: Checking A/C Pressure Sensor Signal Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the C1 FCM 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?

Yes
1. Repair the short to battery voltage in the (C18) A/C Pressure Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 4).
4) (C18) A/C PRESSURE SIGNAL CIRCUIT OPEN

Fig 3: Checking A/C Pressure Sensor Signal Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Measure the resistance of the (C18) A/C Pressure Signal circuit from the A/C Pressure Transducer harness connector to the C1 FCM harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Go To step 5).
No
1. Repair the open in the (C18) A/C Pressure Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
5) (C18) A/C PRESSURE SIGNAL CIRCUIT SHORTED TO THE (F891) 5-VOLT SUPPLY CIRCUIT

Fig 4: Checking A/C Pressure Sensor Signal Circuit & 5-Volt Supply Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance between the (C18) A/C Pressure Signal circuit and the (F891) 5-volt Supply circuit in the A/C Pressure Transducer harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Repair the short between the (F891) 5-volt Supply circuit and the (C18) A/C Pressure Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 6).
6) (C918) SENSOR RETURN CIRCUIT OPEN

Fig 5: Checking A/C Pressure Sensor Return Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Disconnect the IPM FCM harness connector.

Measure the resistance of the (C918) Sensor Return circuit from the A/C Pressure Sensor harness connector to the IPM FCM harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Go To step 7).
No
1. Repair the open in the (C918) Sensor Return circuit
2. Perform POWERTRAIN VERIFICATION TEST .
7) FRONT CONTROL MODULE
NOTE: Before continuing, check the FCM 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 there any problems found?

Yes
1. Repair as necessary.
2. Perform BODY VERIFICATION TEST - VER 1 .
No
1. Replace and program the Front Control Module per Service Information.
2. Perform BODY VERIFICATION TEST - VER 1 .