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 LIMITED, 4.7 P, 4WDREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTCOMMUNICATION DEVICESHEATED SEAT MODULE (HSM) - ELECTRICAL DIAGNOSTICSDTC TROUBLESHOOTINGU0019-CAN B BUSDIAGNOSTIC TEST

2009 Jeep Commander Limited, 4.7 P, 4WD

Diagnostic Test

2009 Jeep Commander Limited, 4.7 P, 4WDSECTION Diagnostic Test

TEST FOR INTERMITTENT CONDITION
1. Turn the ignition on.
2. With the scan tool, record and erase DTCs
3. Cycle the ignition from on to off three times.
4. Turn the ignition on.
5. With the scan tool, read DTCs.
  Does the scan tool display U0019 CAN B BUS CIRCUIT?
  
  Yes
  - Go to step 2
  No
  - The conditions that caused this code to set are not present at this time. Using the SYSTEM WIRING DIAGRAMS as a guide, inspect the wiring and connectors.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
CHECK FRONT CONTROL MODULE DTCs
1. With the scan tool, read Front Control Module DTC's
  Does the scan tool display any CAN B BUS DTCs - ACTIVE?
  
  Yes
  - Refer to the appropriate diagnostic procedure. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Diagnosis and Testing .
  No
  - Go to step 3
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 Heated Seat Module connector.
3. Disconnect the Front Control Module C1 connector.
4. Measure the resistance of the (D55) Can B Bus (+) circuit between the Front Control Module C1 connector and the Heated Seat Module connector.
  Is the resistance below 2.0 ohms?
  
  Yes
  - Go to step 4
  No
  - Repair the Can B Bus (+) circuit for an open.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
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 Heated Seat Module connector.
  Is the resistance below 2.0 ohms?
  
  Yes
  - Replace the Heated Seat Module.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
  No
  - Repair the 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.