P0588 HIGH VOLTAGE DETECTED AT THE SPEED CONTROL VENT DRIVER

When Monitored and Set Condition:

When Monitored: While the engine is running and the Speed control is set.
Set Condition: The Speed control vent commanded state is on and the feedback state is off.

POSSIBLE CAUSES

• SPEED CONTROL SERVO ASSEMBLY
• (V35) SPEED CONTROL VENT SHORTED TO VOLTAGE
• (V35) SPEED CONTROL VENT CIRCUIT SHORTED TO OTHER CIRCUITS
• ECM
• INTERMITTENT CONDITION
• SPEED CONTROL SERVO

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 Speed Control Vacuum Solenoid. Using a 12-volt test light connected to battery positive, check the Speed Control Vacuum Solenoid Output circuit in the Speed Control Assembly 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.
   Turn the ignition on. Measure the voltage of the Speed Control vent circuit between the Cruise Control Assembly harness connector and engine ground. Is the voltage above 1 volt?
   Yes --> Repair the Speed Control vent circuit for a short to voltage.
   No --> Go To 3
3. Turn the ignition off. Measure the resistance between the Speed Control Vacuum circuit and all other circuits in the ECM connectors. Is the resistance less than 10 ohms?
   Yes --> Repair the (V35) Speed Control vent circuit shorted to other circuit.
   No --> Go To 4
4. Reconnect the ECM harness connectors. Ignition on, engine not running. With the DRBIII®, actuate the Speed Control Vent Solenoid. Using a 12-volt test light connected to battery positive, check the Speed Control Vent Solenoid Output circuit in the Speed Control Assembly 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 5
   No --> Replace and program the ECM in accordance with the Service Information.
5. Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
   Where any problems found?
   Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
   No --> Replace the Cruise control servo.