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, 5.7 T, RWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTANTI-THEFT SYSTEMS(CABIN COMPARTMENT NODE (CCN) - ELECTRICAL DIAGNOSTICS)DTC TROUBLESHOOTINGU1121-LOST COMMUNICATION WITH LIN ECU 1DIAGNOSTIC TEST

2009 Jeep Commander Limited, 5.7 T, RWD

Diagnostic Test

2009 Jeep Commander Limited, 5.7 T, RWDSECTION Diagnostic Test

CHECK FOR AN ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, record and erase DTCs.
3. Wait 30 seconds.
4. 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 chaffed, 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 VOLTAGE AT ELECTRONIC OVERHEAD MODULE

Fig 1: Checking Voltage At Electronic Overhead Module
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the EOM harness connector.
3. Turn the ignition on.
4. Check the voltage of the (A114) Fused B+ (I.O.D.) circuit.
  Is the voltage above 10 volts?
  
  Yes
  - Go to step 3
  No
  - Repair the (A114) Fused B+ (I.O.D.) circuit for an open.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
CHECK GROUND CIRCUIT

Fig 2: Checking Ground Circuit
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Measure the resistance between ground and the (Z915) Ground circuit.
  Is the resistance above 10K ohms?
  
  Yes
  - Repair the (Z915) Ground circuit for an open.
  - Perform the BODY VERIFICATION TEST. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
  No
  - Go To step 4
CHECK LIN BUS CIRCUIT FOR AN OPEN

Fig 3: Checking LIN BUS Circuit For An Open
Courtesy of CHRYSLER LLC
1. Disconnect the Cluster C1 harness connector.
2. Measure the resistance of the (D500) LIN Bus circuit.
  Is the resistance below 10K ohms?
  
  Yes
  - Replace the Cluster 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 (D500) LIN 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.