P0593
SYMPTOM
P0593 SPEED CONTROL SWITCH 2 CIRCUIT HIGH
WHEN MONITORED
With the ignition key on.
SET CONDITION
Speed Control Switch No.2 input above the maximum acceptable voltage at the PCM. One trip fault.
POSSIBLE CAUSES
- (V38) S/C SIGNAL NO.2 CIRCUIT SHORTED TO VOLTAGE
- (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT OPEN BETWEEN THE PCM AND CLOCKSPRING
- (V937) SWITCH RETURN CIRCUIT OPEN BETWEEN PCM AND CLOCKSPRING
- (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT OPEN BETWEEN THE CLOCKSPRING AND S/C SWITCH
- (V937) SWITCH RETURN CIRCUIT OPEN BETWEEN CLOCKSPRING AND S/C SWITCH CLOCKSPRING
- SPEED CONTROL SWITCH
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures
DIAGNOSTIC TEST
1. SPEED CONTROL SWITCH VOLTAGE HIGH
Note: Do not press any of the Speed Control Switch buttons.
Ignition on, engine not running.
With a scan tool, read the Speed Control voltage.
Is the Speed Control voltage above 4.8 volts?
Yes>> Go To 2
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4. Powertrain Verification Test - Ver 4
2. SPEED CONTROL SWITCHES
Disconnect and remove the Speed Control Switches from the steering wheel.
Measure the resistance across each Speed Control Switch.
Monitor the ohmmeter while pressing each function button on each switch.
The following resistance specs are taken between terminals (V38) S/C Switch No.2 Signal and (V937) S/C Switch Return circuits of the Switch when holding the switch button in the following position.
Not pressing any switch - 20.5 k ohms
On/Off- 8.87 k ohms
Set- 0.825 k ohms
Coast- 0.47 k ohms
Cancel - 3.92 k ohms
Resume/Accel - 1.87 k ohms
Does the function on the Speed Control Switches have the correct resistance value?
Yes>> Go To 3
No>> Replace the Speed Control Switch that had the incorrect resistance value. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
3. CLOCKSPRING
Disconnect the upper and lower Clockspring harness connector per Service Information.
Measure the resistance of the (V937) Switch Return circuit between the upper and lower clockspring harness connectors.
Measure the resistance of the (V38) S/C Switch No.2 Signal circuit between the upper and lower clockspring harness connectors.
Was the resistance above 5.0 ohms for either circuit?
Yes>> Replace the clockspring. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 4
4. (V38) SIGNAL NO.2 CIRCUIT SHORTED TO BATTERY VOLTAGE
Connect the Clockspring harness connectors per Service Information. Disconnect the PCM harness connectors.
Measure the voltage on the (V38) S/C Signal No.2 circuit in the Speed Control harness connector.
Ignition on, engine not running.
Is the voltage above 5.2 volts?
Yes>> Repair the short to battery voltage in the (V38) S/C Signal No.2 circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 5
5. (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT OPEN BETWEEN PCM AND CLOCKSPRING
Turn the ignition off.
Disconnect the upper and lower Clockspring harness connectors per Service Information.
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 (V38) S/C Switch No.2 Signal circuit from the lower Clockspring harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms?
Yes>> Go To 6
No>> Repair the open in the (V38) S/C Switch No.2 Signal circuit between the PCM and Clockspring. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
6. (V937) SENSOR GROUND CIRCUIT OPEN BETWEEN THE PCM AND CLOCKSPRING
Measure the resistance of the (V937) Sensor ground circuit from the lower Clockspring harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms?
Yes>> Go To 7
No>> Repair the open in the (V937) Switch Return circuit between the PCM and Clockspring. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
7. (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT OPEN BETWEEN THE CLOCKSPRING AND S/C SWITCH
Measure the resistance of the (V38) S/C Switch No.2 Signal circuit from the upper Clockspring harness connector to the On/Off switch harness connector.
Is the resistance below 5.0 ohms?
Yes>> Go To 8
No>> Repair the open in the (V38) S/C Switch No.2 Signal circuit between the Clockspring and S/C Switch. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
8. (V937) SWITCH RETURN CIRCUIT OPEN BETWEEN THE CLOCKSPRING AND S/C SWITCH
Measure the resistance of the (V937) Switch Return circuit from the On/Off Switch harness connector to the upper Clockspring harness connector.
Is the resistance below 5.0 ohms?
Yes>> Go To 9
No>> Repair the open in the (V937) Switch Return circuit between the Clockspring and S/C Switch. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
9. SPEED CONTROL SWITCH VOLTAGE VALUES
Allow the engine to idle.
With a scan tool, monitor the S/C Switch voltage readings.
Take these same voltage measurements with a voltmeter by back probing the (V38) S/C Switch No.2 Signal circuit at the switches. Compare the voltage readings on the voltmeter to what the scan tool displayed.
Are the voltage readings out of the listed specification and is there less than a 0.2 of a volt difference between the voltmeter switch values and the scan tool switch values?
Yes>> Replace the Speed Control Switch. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go to 10.
10. PCM
Note: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes>> Repair as necessary. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.