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 PERFORMANCEIGNITION SYSTEM(FRONT CONTROL MODULE (FCM) - ELECTRICAL DIAGNOSTICS)DTC TROUBLESHOOTINGB1644-REAR LEFT TURN CONTROL CIRCUIT HIGHDIAGNOSTIC TEST

2009 Jeep Grand Cherokee Laredo, 4.7 P, RWD

Diagnostic Test

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

TEST FOR INTERMITTENT CONDITION
1. Turn the ignition on.
2. With the scan tool, erase all FCM DTCs.
3. Turn the Left Turn Signal on.
4. With the scan tool, read DTCs.
  Does the scan tool display: B1644-REAR LEFT TURN CONTROL CIRCUIT HIGH?
  
  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. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure
INSPECT LEFT REAR TURN SIGNAL BULB
1. Turn the ignition off.
2. Inspect the Left Rear Turn Signal Bulb Assembly.
  Is the inoperative bulb okay?
  
  Yes
  - Go to step 3
  No
  - Replace the Inoperative bulb in accordance with the service information.
  - 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 VOLTAGE
1. Turn the Left Turn Signal off.
2. Disconnect the Left Rear Turn Stop Tail Lamp connector.
3. Turn the ignition on.
4. Measure the voltage of the (L63) Left Rear Turn Signal Control circuit between the Left Rear Turn Stop Tail Lamp connector and ground.
  Is there any voltage present?
  
  Yes
  - Repair the (L63) Left Rear Turn Signal Control circuit for a short to voltage.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure
  No
  - Go to step 4
CHECK (L63) LEFT REAR TURN SIGNAL CONTROL CIRCUIT IN BODY HARNESS FOR AN OPEN

Fig 1: Checking Left Rear Turn Signal Control Circuit In Body Harness For An Open
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the IPM C2 connector.
3. Measure the resistance of the (L63) Left Rear Turn Signal Control circuit between the Left Rear Turn Stop Tail Lamp connector and the IPM C2 connector.
  Is the resistance above 5.0 ohms?
  
  Yes
  - Repair the (L63) Left Rear Turn Signal Control circuit for an open.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure
  No
  - Go to step 5
CHECK (L63) LEFT REAR TURN SIGNAL CONTROL CIRCUIT IN IPM FOR A SHORT TO VOLTAGE

Fig 2: Checking Left Rear Turn Signal Control Circuit In IPM For A Short To Voltage
Courtesy of CHRYSLER LLC
1. Disconnect the Front Control Module (FCM) from the IPM 49-way connector.
2. Turn the ignition on.
3. Measure the voltage of the (L63) Left Rear Turn Signal Control circuit between the IPM 49-way connector and ground.
  Is there any voltage present?
  
  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
  - Go to step 6
CHECK (L63) LEFT REAR TURN SIGNAL CONTROL CIRCUIT IN IPM FOR AN OPEN
1. Measure the resistance of the (L63) Left Rear Turn Signal Control circuit between the IPM 49-way connector and IPM C2 connector (at IPM).
  Is the resistance above 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.