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 MANUALSJEEP2008GRAND CHEROKEE SRT-8REPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTCOMMUNICATION DEVICESAUTOMATIC HIGHBEAM MODULE (AHBM) - ELECTRICAL DIAGNOSTICSDTC TROUBLESHOOTINGU0019-CAN B BUSDIAGNOSTIC TEST

2008 Jeep Grand Cherokee SRT-8

Diagnostic Test

2008 Jeep Grand Cherokee SRT-8SECTION Diagnostic Test

CHECK FOR AN ACTIVE DTC
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.
  Is the DTC active?
  
  Yes
  - Go to step 2
  No
  - The condition that caused this code to set is not present at this time. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, and partially broken wires. Also inspect the related connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals.
  - 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 DTCs.
  Does the scan tool display the U0019-CAN B BUS DTC?
  
  Yes
  - Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Diagnosis and Testing and perform the U0019-CAN B BUS 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.
  NOTE: The Auto High Beam Module is part of the Right High Intensity Discharge Lamp.
3. Disconnect the Right High Intensity Discharge Lamp harness connector.
4. Disconnect the Front Control Module C1 harness connector.
5. Measure the resistance of the (D55) Can B Bus (+) circuit between the Front Control Module C1 harness connector and the Right High Intensity Discharge Lamp harness 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 harness connector and the Right High Intensity Discharge Lamp harness connector.
  Is the resistance below 2.0 Ohms?
  
  Yes
  - Replace the Right High Intensity Discharge Lamp 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 (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.