Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSJEEP2009COMMANDER SPORT, 3.7 K, RWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTCOMMUNICATION DEVICESSUNROOF MODULE (SUNR) - ELECTRICAL DIAGNOSTICSDTC TROUBLESHOOTINGU0019-CAN B BUSDIAGNOSTIC TEST

2009 Jeep Commander Sport, 3.7 K, RWD

Diagnostic Test

2009 Jeep Commander Sport, 3.7 K, RWDSECTION Diagnostic Test

CHECK FOR ACTIVE DIAGNOSTIC TROUBLE CODES (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. Turn the ignition off and wait 30 seconds.
4. Turn the ignition on.
5. 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 DTCs - ACTIVE?
  
  Yes
  - Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Diagnosis and Testing and perform the appropriate diagnostic procedure.
  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 Sunroof Motor/Module 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 Sunroof Motor/Module connector.
  Is the resistance below 2.0 Ohms?
  
  Yes
  - Go to step 4
  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
(D54) CAN B BUS (-) CIRCUIT OPEN

Fig 2: Checking CAN B BUS (-) Circuit Open
Courtesy of CHRYSLER LLC
1. Measure the resistance of the (D54) CAN B Bus (-) circuit between the Front Control Module C1 connector and the Sunroof Motor/Module connector.
  Is the resistance below 2.0 Ohms?
  
  Yes
  - Replace the Sunroof Motor/Module in accordance with the Service Information.
  - Perform the Sunroof Position Calibration. Refer to Electrical - Power Systems/Power Top/MOTOR, Sunroof - Standard Procedure . Perform the Excessive Force Limitation Calibration. Refer to Electrical - Power Systems/Power Top/MOTOR, Sunroof - Standard Procedure .
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure
  No
  - Repair the (D54) CAN B Bus (-) circuit for an open.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.