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 DIAGNOSISTRANSMISSIONTRANSFER CASE(FINAL DRIVE CONTROL MODULE (FDCM) - ELECTRICAL DIAGNOSTICS)DTC TROUBLESHOOTINGC1421-REAR DIFFERENTIAL CLUTCH PERFORMANCEDIAGNOSTIC TEST

2009 Jeep Commander Limited, 4.7 P, 4WD

Diagnostic Test

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

ACTIVE DTC
NOTE: You must diagnose any Solenoid circuit (Low or High) DTCs first if set along with this DTC before continuing.
1. Ignition on, engine not running.
2. With the scan tool, read DTCs.
  Is the DTC active at this time?
  
  Yes
  - Go to step 2
  No
  - Go To step 4
WIRING HARNESS INSPECTION
1. Inspect the wiring harness from both solenoids to the FDCM. Ensure that the harness has routed correctly.
2. Inspect the FDCM harness connector and Differential Solenoid connectors. Ensure the terminals are clean and no damage is present.
  Was the wiring harness and connectors OK?
  
  Yes
  - Go to step 3
  No
  - Repair as necessary.
  - Perform FDCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Final Drive Control (FDCM) - Standard Procedure .
INSPECTION DIFFERENTIAL
1. Ensure the Differential is operating properly. Refer to DIFFERENTIAL AND DRIVELINE .
2. Inspect the Differential for external fluid leaks. Repair as necessary, refer to DIFFERENTIAL AND DRIVELINE .
  Is the Differential operating properly?
  
  Yes
  - Replace the Rear Differential Solenoid in accordance with the service information.
  - Perform FDCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Final Drive Control (FDCM) - Standard Procedure .
  No
  - Repair as necessary.
  - Perform FDCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Final Drive Control (FDCM) - Standard Procedure .
INTERMITTENT WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle test the wiring harness and connectors while checking for shorted and open circuits.
4. Using the scan tool, monitor the data related to this circuit while performing the wiggle test. Look for the data to change or for the DTC to reset.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform FDCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Final Drive Control (FDCM) - Standard Procedure .
  No
  - Test complete.

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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.