P0596 HIGH 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 Speed Control Servo is below a calibrated value for a calibrated
amount on time.

POSSIBLE CAUSES

• SPEED CONTROL SERVO ASSEMBLY
• (V32) S/C 12-VOLT SOURCE SHORTED TO OTHER CIRCUITS
• (V32) S/C BRAKE SWITCH OUTPUT SHORTED TO GROUND
• ECM
• INTERMITTENT CONDITION

DIAGNOSTIC PROCEDURE

1. Turn the ignition off. Disconnect the Speed control servo harness connector.
   NOTE: Check connectors - Clean/repair as necessary.
   Ignition on, engine not running. With the DRBIII®, actuate the S/C 12-volt source. Using a 12-volt test light connected to battery 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 --> Replace the speed control servo assembly.
   No --> Go To 2
2. Turn the ignition off. Disconnect the ECM harness connector(s).
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance of the S/C brake switch output circuit between the Speed Control assembly connector and battery negative. Is the resistance greater than 100k Ohms?
   Yes --> Go To 3
   No --> Repair the (V32) S/C brake switch output shorted to ground.
3. 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 100k Ohms?
   Yes --> Go To 4
   No --> Repair the (V32) S/C 12-volt source circuit shorted to other circuit.
4. Turn the ignition off. 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 battery 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 --> Test Complete.
   No --> Replace and program the ECM in accordance with the Service Information.