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Home >> Jeep >> 2007 >> Commander Base, 4.7 P, AWD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> DTCS P0581 To P0643 >> P0594-Speed Control Servo Power Relay Circuit >> Diagnostic Test
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Diagnostic Test

  1. 1) ACTIVE DTC 
    NOTE: If this code is setting on a vehicle that doesn't have a S/C Servo, flash the correct code into the PCM or the wrong PCM may have previously been installed.

    Ignition on, engine not running.

    With a scan tool, select View DTCs.

    Is the DTC Active at this time? 

    Yes 

    1. Go to  2).

    No 

    1. Refer to INTERMITTENT CONDITION Diagnostic Procedure.
  2. 2) (V32) S/C SUPPLY CIRCUIT 
    Fig 1: Checking Speed Control Brake Switch Supply Circuit
    GC0027164Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Disconnect the Stop Lamp Switch harness connector.

    Ignition on, engine not running. (It may be necessary to start the engine.)

    Using a 12-volt test light connected to ground, probe the (V32) S/C Supply circuit in the Switch harness connector while holding the Cruise Switch in the ON position.

    Does the test light illuminate brightly? 

    Yes 

    1. Go to  3).

    No 

    1. Go to  7).
  3. 3) STOP LAMP SWITCH 

    Disconnect and remove the Stop Lamp Switch.

    Measure the resistance across the (V32) S/C Supply circuit terminal and the (V30) S/C Brake Switch Output circuit terminal in the Stop Lamp Switch.

    Push the Plunger of the Switch in and let it out.

    Does the resistance change from below 5.0 ohms to an open circuit? 

    Yes 

    1. Go to  4).

    No 

    1. Replace the Stop Lamp Switch.
    2. Perform POWERTRAIN VERIFICATION TEST .
  4. 4) (V30) S/C BRAKE SWITCH OUTPUT 
    Fig 2: Checking Speed Control Brake Switch Output Circuit
    GC0027163Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Connect the Stop Lamp Switch harness connector and install the Switch.

    Disconnect the Speed Control Servo harness connector.

    Ignition on, engine not running.

    NOTE: It is necessary to PRESS and HOLD the Speed Control Switch in the ON position while checking for voltage.

    Using a 12-volt test light connected to ground, probe the (V30) S/C Brake Switch Output circuit in the Servo Harness connector.

    Does the test light illuminate brightly? 

    Yes 

    1. Replace the S/C Servo.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  5).
  5. 5) (V30) S/C BRAKE SWITCH OUTPUT CIRCUIT OPEN 
    Fig 3: Checking Speed Control Brake Switch Output Circuit For Open
    GC0027178Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Disconnect the Brake Lamp Switch harness connector.

    Measure the resistance of the (V30) S/C Brake Switch Output circuit from the Stop Lamp Switch harness connector to the S/C Servo harness connector.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Repair the excessive resistance in the (V30) S/C Brake Switch Output circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  6).
  6. 6) (V30) S/C BRAKE SWITCH OUTPUT CIRCUIT SHORTED TO GROUND 
    Fig 4: Checking S/C Brake Switch Output Circuit For Short To Ground
    GC0002992Courtesy of CHRYSLER LLC

    Measure the resistance between ground and the (V30) S/C Brake Switch Output circuit in the Speed Control Servo harness connector.

    Is the resistance below 100 ohms? 

    Yes 

    1. Repair the short to ground in the (V30) S/C Brake Switch Output circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  9).
  7. 7) (V32) S/C SUPPLY CIRCUIT OPEN 
    Fig 5: Checking Speed Control Brake Switch Supply Circuit For Open
    GC0027165Courtesy of CHRYSLER LLC

    Turn the ignition off.

    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 (V32) S/C Supply circuit from the Stop Lamp Switch harness connector to the appropriate terminal of special tool #8815.

    Is the resistance above 5.0 ohms? 

    Yes 

    1. Repair the open in the (V32) S/C Supply circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  8).
  8. 8) (V32) S/C SUPPLY CIRCUIT SHORTED TO GROUND 
    Fig 6: Checking Speed Control Brake Switch Supply Circuit For Short To Ground
    GC0027146Courtesy of CHRYSLER LLC

    Measure the resistance between ground and the (V32) S/C Supply circuit in the Stop Lamp Switch harness connector.

    Is the resistance below 100 ohms? 

    Yes 

    1. Repair the short to ground in the (V32) S/C Supply circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  9).
  9. 9) 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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