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 MANUALSJEEP2010GRAND CHEROKEE LIMITED, 5.7 T, 4WDREPAIR AND DIAGNOSISENGINE PERFORMANCEENGINE CONTROL SYSTEMS(FRONT CONTROL MODULE (FCM) - ELECTRICAL DIAGNOSTICS)DTC TROUBLESHOOTINGB1668-REVERSE LAMP CONTROL CIRCUIT HIGHDIAGNOSTIC TEST

2010 Jeep Grand Cherokee Limited, 5.7 T, 4WD

Diagnostic Test

2010 Jeep Grand Cherokee Limited, 5.7 T, 4WDSECTION Diagnostic Test

TEST FOR INTERMITTENT CONDITION
1. Turn the ignition on.
2. With the scan tool, clear all FCM DTCs.
3. Shift the transmission into reverse.
4. With the scan tool, read DTCs.
  Does the scan tool display: B1668-REVERSE LAMP 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 wiring diagram/schematic as a guide, inspect the wiring and connectors.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
(L1) BACK-UP LAMP FEED CIRCUIT SHORT TO VOLTAGE

Fig 1: Checking Back-Up Lamp Feed Circuit Short To Voltage
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the IPM C2 harness connector.
3. Turn the ignition on.
4. Measure the voltage on the (L1) Back-up Lamp Feed circuit.
  Is the voltage greater than 10.0 volts?
  
  Yes
  - Repair the short to voltage in the (L1) Back-up Lamp Feed circuit.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
  No
  - Go to step 3
CHECK (L1) BACK-UP LAMP FEED CIRCUIT IN IPM FOR A SHORT TO BATTERY VOLTAGE

Fig 2: Checking Back-Up Lamp Feed Circuit For A Short To Battery Voltage
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the Front Control Module (FCM) from the IPM 49-way connector.
3. Reconnect the IPM C2 harness connector.
4. Measure the voltage between ground and the (L1) Back-up Lamp circuit.
  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
  - 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.