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HOMESERVICE MANUALSJEEP2008GRAND CHEROKEE OVERLAND, 5.7 2, 4WDREPAIR AND DIAGNOSISHEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSDTCS B1001 TO B10A2B106C-REAR DEFROST CONTROL CIRCUIT HIGH (ATC)DIAGNOSTIC TEST
2008 Jeep Grand Cherokee Overland, 5.7 2, 4WD

Diagnostic Test

2008 Jeep Grand Cherokee Overland, 5.7 2, 4WDSECTION Diagnostic Test
  1. INSTALL A SUBSTITUTE REAR WINDOW DEFOGGER RELAY & THEN CHECK FOR DTC B106C-REAR DEFROST CONTROL CIRCUIT HIGH 
    Fig 1: Identifying EBL Relay Terminals
    GC0028224Courtesy of CHRYSLER LLC

    Turn the ignition on.

    Verify that the EBL mode switch is off.

    Turn the ignition off.

    Install a substitute Rear Window Defogger Relay.

    Turn the ignition on.

    With the scan tool, erase HVAC DTCs.

    Turn the ignition off, wait 10 seconds, and turn the ignition on.

    Press the EBL mode switch is on.

    With the scan tool, read HVAC DTCs.

    Does the scan tool display: B106C-REAR DEFROST CONTROL CIRCUIT HIGH? 

    Yes 

    1. Go To  2.

    No 

    1. Replace the original Rear Window Defogger Relay in accordance with the Service Information.
    2. Perform BODY VERIFICATION TEST .
  2. CHECK (C115) REAR WINDOW DEFOGGER RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE 
    Fig 2: Checking Rear Window Defogger Relay Control Circuit For Short To Voltage
    GC0028253Courtesy of CHRYSLER LLC

    Turn the ignition on.

    Verify that the EBL mode switch is off.

    Turn the ignition off.

    Remove the substitute Rear Window Defogger Relay.

    Disconnect the A/C Heater Control C1 harness connector.

    Turn the ignition on.

    Measure the voltage of the (C115) Rear Window Defogger Relay Control circuit.

    Is the voltage above 0.2 volts? 

    Yes 

    1. Repair the (C115) Rear Window Defogger Relay Control circuit for a short to voltage. Reinstall the original Rear Window Defogger Relay.
    2. Perform BODY VERIFICATION TEST .

    No 

    1. Go To  3.
  3. CHECK (C115) REAR WINDOW DEFOGGER RELAY CONTROL CIRCUIT FOR AN OPEN 
    Fig 3: Checking Rear Window Defogger Relay Control Circuit For Open
    GC0028252Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Measure the resistance of the (C115) Rear Window Defogger Relay Control circuit between the Rear Window Defogger Relay connector terminal 85 in the JB and the A/C Heater Control C1 harness connector.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Replace the A/C Heater Control in accordance with the Service Information. Reinstall the original Rear Window Defogger Relay.
    2. Perform BODY VERIFICATION TEST .

    No 

    1. Repair the (C115) Rear Window Defogger Relay Control circuit for an open. Reinstall the original Rear Window Defogger Relay.
    2. Perform BODY VERIFICATION TEST .
RENDER: 1.0x

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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.