Diagnostic Test

WARNING: This page is about a different car, the 2009 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

CHECK FOR ACTIVE DTCS
1. With the scan tool, read the active DTCs.
2. Cycle the ignition switch from off to on at least 5 times, leaving the ignition on for a minimum of 90 seconds per cycle.
3. With the scan tool, read the active DTCs.
  Does the scan tool display this DTC as active?
  
  Yes
  - Go to step 2
  No
  - 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.
CHECK FRONT CONTROL MODULE DTCs
1. With the scan tool, read Front Control Module active DTCs
  Does the scan tool display any CAN B BUS DTC's - ACTIVE?
  
  Yes
  - Go to and perform the appropriate diagnostic test. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Diagnosis and Testing .
  No
  - Go to step 3
(D55) CAN B BUS (+) CIRCUIT OPEN

Fig 1: Checking CAN B BUS (+) Circuit Open
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the negative battery cable.
3. Disconnect the Driver Door Module C2 connector.
4. Disconnect the Front Control Module C1 connector.
5. Measure the resistance of the (D55) CAN B Bus (+) circuit between the Front Control Module C1 connector and the Door Module C2 connector.
  Is the resistance below 2.0 ohms?
  
  Yes
  - Replace the Driver Door Module in accordance with the Service Information.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
  No
  - Repair the (D55) CAN B Bus (+) circuit for an open.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .