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) VERIFY DTC IS ACTIVE
NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.

With the scan tool, read active DTC's.

Is this DTC active?

Yes
1. Go To 2).
No
1. Refer to the Stored Lost Communication test procedure. Refer to DIAGNOSTIC CODE INDEX .
2) CHECK FOR ANY OF THE FOLLOWING ACTIVE DTC'S
With the scan tool, read active DTC's from all modules.

NOTE: Check for FCM configuration, CAN B or C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTC's.

Does the scan tool display any active DTC's to the conditions listed above?

Yes
1. Diagnose and repair the DTC. Refer to DIAGNOSTIC CODE INDEX for a complete list of the symptoms.
No
1. Go To 3).
3) VERIFY THAT THE TIRM IS ACTIVE ON THE BUS
Turn the ignition on.

With the scan tool, select Network View and select Advanced.

NOTE: A red X will be next to the module that is not communicating, indicating that the module is not active on the Bus network. A green check indicates that the module is active on the Bus network.

Verify that the TM is active on the bus.

Is the TM active on the bus?

Yes
1. Replace and program the Front Control Module in accordance with the service information.
2. Perform BODY VERIFICATION TEST - VER 1 .
No
1. Go To 4).
4) (A922) (A907) FUSED B(+) CIRCUITS OPEN

Fig 1: Checking Fused B (+) Circuits
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the Trailer Lighting Module C2 harness connector.

Using a 12-volt test light connected to ground, check the (A922) and (A907) Fused B(+) circuits.

Does the test light illuminate brightly on each circuit?

Yes
1. Go To 5).
No
1. Repair the (A922) or (A907) Fused B(+) circuit for an open or short.
2. Perform BODY VERIFICATION TEST - VER 1 .
5) (F941) FUSED IGNITION SWITCH OUTPUT (RUN-START) CIRCUIT OPEN

Fig 2: Checking Fused Ignition Switch Output (RUN-START) Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition on.

Disconnect the Trailer Lighting Module C4 harness connector.

Using a 12-volt test light connected to ground, check the (F941) Fused Ignition Switch Output circuit.

Does the test light illuminate brightly?

Yes
1. Go To 6).
No
1. Repair the (F941) Fused Ignition Switch Output circuit for an open or short.
2. Perform BODY VERIFICATION TEST - VER 1 .
6) (Z923) GROUND CIRCUIT OPEN

Fig 3: Checking Ground Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Using a 12-volt test light connected to 12-volts, check the (Z923) ground circuit.

Does the test light illuminate brightly?

Yes
1. Go To 7).
No
1. Repair the (Z923) ground circuit for an open.
2. Perform BODY VERIFICATION TEST - VER 1 .
7) (D55) AND (D54) CAN B BUS CIRCUITS OPEN

Fig 4: Checking CAN B BUS Circuits
Courtesy of DAIMLERCHRYSLER CORP.

NOTE: One open circuit will not cause this condition.

Measure the voltage between the (D54) CAN B Bus (-) circuit and ground.

Measure the voltage between the (D55) CAN B Bus (+) circuit and ground.

Is there any voltage present on either circuit?

Yes
1. Replace the Trailer Lighting Module in accordance with the service information.
2. Perform BODY VERIFICATION TEST - VER 1 .
No
1. Repair the (D55) and (D54) CAN B Bus circuits for an open. Inspect the connector for damage.
2. Perform BODY VERIFICATION TEST - VER 1 .