Diagnostic Test

WARNING: This page is about a different car, the 2006 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

1) CHECK FOR ACTIVE DTC
With the scan tool, read the active DTC's.

Cycle the ignition switch from off to on, leaving the ignition on for a minimum of 90 seconds.

With the scan tool, read the active DTC's.

Does the scan tool display this DTC as active?

Yes
1. Go To 2).
No
1. If the DTC is stored, check for an intermittent condition. Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.
2) A/C PRESSURE TRANSDUCER
Turn the ignition off.

Disconnect the A/C Pressure Transducer harness connector.

Cycle the ignition switch from off to on, leaving the ignition on for a minimum of 90 seconds.

With the scan tool, read the active DTC's.

Does the scan tool display this DTC as active?

Yes
1. Go To 3).
No
1. Replace the A/C Pressure Transducer in accordance with the service information.
2. Perform BODY VERIFICATION TEST - VER 1 .
3) (F891) 5 VOLT SUPPLY CIRCUIT SHORTED TO GROUND

Fig 1: Checking 5 Volt Supply Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the FCM C1 harness connector.

Measure the resistance between ground and the (F891) 5 Volt Supply circuit.

Is the resistance below 1000.0 ohms?

Yes
1. Repair the (F891) 5 Volt Supply circuit for a short to ground.
2. Perform BODY VERIFICATION TEST - VER 1 .
No
1. Inspect the wiring and connectors for damage or shorted circuits. If OK, replace and program the Front Control Module in accordance with the service information.
2. Perform BODY VERIFICATION TEST - VER 1 .