P0594

P0594-SPEED CONTROL SERVO POWER CIRCUIT





For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
Ignition on. Speed Control active.

- Set Condition:
The PCM detects a open or short in the Speed Control Power Supply circuit. One Trip Fault.





Diagnostic Test

1. SPEED CONTROL VACUUM CONTROL
Ignition on, engine not running.
With the scan tool read DTCs and record the related Freeze Frame data.
With the scan tool actuate the Speed Control Vacuum Solenoid and note operation.
Does the Speed Control Vacuum Solenoid actuate properly?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure.Intermittent Condition
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To2

2. (V397) S/C BRAKE SWITCH OUTPUT CIRCUIT
Turn the ignition off.
Disconnect the S/C Servo harness connector.
Turn the ignition on.
Using the scan tool actuate the S/C Vacuum Solenoid.
Using a test light connected to ground, probe the (V397) S/C Brake Switch Output circuit in the S/C Servo harness connector.
Does the test light illuminate brightly and flash on and off?

Yes

- Go To6

No

- Go To3

3. (V32) S/C SUPPLY CIRCUIT
Turn the ignition off.
Disconnect the Stop Lamp Switch harness connector.
Turn the ignition on.
Using the scan tool actuate the S/C Vacuum Solenoid.
Using a test light connected to ground, probe the (V32) S/C Supply circuit in the Brake Switch harness connector.
Does the test light illuminate brightly?

Yes

- Go To4

No

- Go To7

4. (V397) S/C BRAKE SWITCH OUTPUT CIRCUIT OPEN




Turn the ignition off.
Measure the resistance of the (V397) S/C Brake Switch Output circuit from the Speed Control Servo harness connector to the Stop Lamp Switch connector.
Is the resistance below 5.0 ohms?

Yes

- Go To5

No

- Repair the open in the (V397) S/C Brake Switch Output circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

5. (V397) S/C BRAKE SWITCH OUTPUT CIRCUIT SHORTED TO GROUND




Measure the resistance between ground and the (V397) S/C Brake Switch Output circuit at the Speed Control Servo harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (V397) S/C Brake Switch Output circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Replace the Stop Lamp Switch.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. (Z902) S/C GROUND CIRCUIT OPEN




Turn the ignition off.
Measure the resistance of the (Z902) S/C Ground circuit at the S/C Servo harness connector to ground.
Is the resistance below 5.0 ohms?

Yes

- Replace the Speed Control Servo.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Repair the open in the (Z902) S/C Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

7. (V32) S/C SUPPLY OPEN




Turn the ignition off.
Disconnect the 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 Brake Lamp Switch harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms?

Yes

- Go To8

No

- Repair the open/high resistance in the (V32) S/C Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

8. (V32) S/C SUPPLY CIRCUIT SHORT TO GROUND




Measure the resistance between ground and the (V32) S/C Supply circuit at the Speed Control Servo harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (V32) S/C Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To9

9. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

If the there are no possible causes remaining, view repair.

Repair

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test