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  • P0595 Low Voltage Detected At The S/C Brake Switch Output

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    P0595 LOW VOLTAGE DETECTED AT THE S/C BRAKE SWITCH OUTPUT

    When Monitored and Set Condition:

    When Monitored: While the key is on.
    Set Condition: The voltage detected on the Cruise Control Servo is above a calibrated value for a calibrated
    amount on time.

    POSSIBLE CAUSES

    • SPEED CONTROL SERVO
    • (V32) S/C 12-VOLT SOURCE CIRCUIT OPEN
    • GROUND CIRCUIT OPEN
    • (V32) S/C 12-VOLT SOURCE SHORTED TO VOLTAGE
    • (V32) S/C 12-VOLT SOURCE SHORTED TO OTHER CIRCUITS
    • ECM
    • INTERMITTENT CONDITION

    DIAGNOSTIC PROCEDURE

    1. Turn the ignition off. Disconnect the Speed Control Servo harness connector
      NOTE: Check connectors - Clean/repair as necessary.
      Turn the ignition on. With the DRBIII®, actuate the S/C 12 volt source. Using a 12-volt test light connected to ground, check the S/C 12-volt source circuit in the Speed Control Servo harness connector.
      NOTE: The test light must illuminate brightly.
      Compare the brightness to that of a direct connection to the battery. Does the test light cycle on and off and illuminate brightly?
      Yes --> Go To 2
      No --> Go To 3
    2. Turn the ignition off. Disconnect the ECM harness connectors.
      NOTE: Check connectors - Clean/repair as necessary.
      Measure the resistance of the ground circuit between the Speed control servo connector and battery negative. Is the resistance less than 10 ohms?
      Yes --> Replace the Speed control servo.
      No --> Repair the open ground circuit at the Cruise control servo harness connector.
    3. Turn the ignition off. Disconnect the ECM harness connectors.
      NOTE: Check connectors - Clean/repair as necessary.
      Measure the resistance of the S/C 12-volt source circuit between the ECM harness connector and the Speed Control servo assembly harness connector. Is the resistance less than 10 Ohms?
      Yes --> Go To 4
      No --> Repair the open (V32) 12-volt source circuit.
    4. Measure the voltage between the S/C 12-volt source circuit in the Speed Control servo assembly harness connector and battery negative. Is the voltage greater than 1 volt?
      Yes --> Repair the (V32) S/C 12-volt source circuit shorted to voltage.
      No --> Go To 5
    5. Measure the resistance between the S/C 12-volt source circuit in the ECM harness connector and all other circuits in the ECM harness connectors. Is the resistance less than 10 Ohms?
      Yes --> Repair the (V32) S/C 12-volt source circuit shorted to other circuit.
      No --> Go To 6
    6. Reconnect the ECM harness connectors. Ignition on, engine not running. With the DRBIII®, actuate the S/C 12-volt source. Using a 12-volt test light connected to ground, check the S/C brake switch output circuit in the Speed Control servo harness connector.
      NOTE: The test light must illuminate brightly.
      Compare the brightness to that of a direct connection to the battery. Does the test light cycle on and off and illuminate brightly?
      Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
      No --> Replace and program the ECM in accordance with the Service Information.

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