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 MANUALSJEEP2009GRAND CHEROKEE LAREDO, 4.7 P, RWDREPAIR AND DIAGNOSISENGINE PERFORMANCETUNE-UP(FRONT CONTROL MODULE (FCM) - ELECTRICAL DIAGNOSTICS)DTC TROUBLESHOOTINGB1643-REAR LEFT TURN CONTROL CIRCUIT LOWDIAGNOSTIC TEST

2009 Jeep Grand Cherokee Laredo, 4.7 P, RWD

Diagnostic Test

2009 Jeep Grand Cherokee Laredo, 4.7 P, RWDSECTION Diagnostic Test

INTERMITTENT CONDITION
1. Turn the ignition on.
2. Using the scan tool, erase all FCM DTCs.
3. Turn the Left Turn Signals on.
4. Using the scan tool, read DTCs.
  Does the scan tool display: B1643-REAR LEFT TURN CONTROL CIRCUIT LOW?
  
  Yes
  - Go to step 2
  No
  - The condition that caused the symptom is currently not present. Inspect the related wiring for a possible intermittent condition. Look for any chafed, pierced, pinched, or partially broken wires.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
CHECK (L63) LEFT REAR TURN SIGNAL CONTROL CIRCUIT IN BODY HARNESS FOR A SHORT TO GROUND

Fig 1: Checking Left Rear Turn Signal Control Circuit In Body Harness For A Short To Ground
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the IPM C2 connector.
3. Disconnect the Left Rear Turn Stop Tail Lamp connector.
4. Measure the resistance of the (L63) Left Rear Turn Signal Control circuit between ground and the IPM C2 connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Repair the (L63) Left Rear Turn Signal Control circuit for a short to ground.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
  No
  - Go to step 3
CHECK (L63) LEFT REAR TURN SIGNAL CONTROL CIRCUIT IN IPM FOR A SHORT TO GROUND

Fig 2: Checking Left Rear Turn Signal Control Circuit In IPM For A Short To Ground
Courtesy of CHRYSLER LLC
1. Disconnect the Front Control Module (FCM) from the IPM 49-way connector.
2. Measure the resistance of the (L63) Left Rear Turn Signal Control circuit between ground and the IPM 49-way connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Replace the Integrated Power Module (IPM) in accordance with the service information.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
  No
  - Replace the Front Control Module (FCM) in accordance with the service information.
  - Perform the BODY VERIFICATION TEST. See 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.