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.