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Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
  1. 1)  ACTIVE DTC 
    NOTE: Make sure the Stop Lamp Switch is adjusted properly before continuing.

    Ignition on, engine not running.

    With a scan tool, read DTCs.

    Is the DTC active at this time? 

    Yes 

    1. Go To step  2).

    No 

    1. Refer to INTERMITTENT CONDITION .
    2. Perform POWERTRAIN VERIFICATION TEST .
  2. 2)  STOP LAMP SWITCH OPERATION 

    Turn the ignition off.

    Disconnect the Stop Lamp Switch harness connector.

    Measure the resistance between the (Z904) Ground circuit terminal and the (B15) Brake Switch No.1 Signal terminal in the Stop Lamp Switch.

    Apply and release the Stop Lamp Switch while monitoring the ohmmeter.

    Does the resistance change from below 5.0 ohms to open circuit when pressing and releasing the brake pedal switch? 

    Yes 

    1. Go To step  3).

    No 

    1. Replace the Stop Lamp Switch.
    2. Perform POWERTRAIN VERIFICATION TEST .
  3. 3)  STOP LAMP SWITCH OPERATION 

    Measure the resistance between the (F942) Fused Ignition Switch terminal and the (B16) Brake Switch No.2 Signal circuit terminal in the Stop Lamp Switch.

    Apply and release the Stop Lamp Switch while monitoring the ohmmeter.

    Does the resistance change from below 5.0 ohms to open circuit when pressing and releasing the Stop Lamp switch? 

    Yes 

    1. Go To step  4).

    No 

    1. Replace the Stop Lamp Switch.
    2. Perform POWERTRAIN VERIFICATION TEST .
  4. 4)  (B15) BRAKE SWITCH NO.1 SIGNAL CIRCUIT OPEN 
    Fig 1: Checking Brake Switch No. 1 Signal Circuit
    GC0027149Courtesy of DAIMLERCHRYSLER CORP.

    Disconnect the C3 PCM harness connector.

    CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

    Measure the resistance of the (B15) Brake Switch No.1 Signal circuit from the Stop Lamp Switch harness connector to the appropriate terminal of special tool #8815.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Go To step  5).

    No 

    1. Repair the open in the (B15) Brake Switch No.1 Signal circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .
  5. 5)  (B16) BRAKE SWITCH NO.2 SIGNAL CIRCUIT OPEN 
    Fig 2: Checking Brake Switch No. 2 Signal Circuit
    GC0027145Courtesy of DAIMLERCHRYSLER CORP.

    Measure the resistance of the (B16) Brake Switch No.2 Signal circuit from the Stop Lamp Switch harness connector to the C1 FCM harness connector.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Go To step  6).

    No 

    1. Repair the open in the (B16) Brake Switch No.2 Signal circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .
  6. 6)  PCM 
    NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

    Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

    Were there any problems found? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Replace and program the Powertrain Control Module per Service Information.
    2. Perform POWERTRAIN VERIFICATION TEST .
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