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P1593





SYMPTOM
P1593-SPEED CONTROL SWITCH 1/2 STUCK

WHEN MONITORED
Ignition on.

SET CONDITION
One of the S/C Switches is mechanically stuck in the On/Off, Resume/Accel, or Set position for too long. One trip fault.

POSSIBLE CAUSES
- (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT OPEN
- (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT OPEN
- (V937) SWITCH RETURN CIRCUIT OPEN
- (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
- (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
- (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO GROUND
- (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT SHORTED TO GROUND
- (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO (V937) S/C SWITCH RETURN CIRCUIT
- (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT SHORTED TO (V937) S/C SWITCH RETURN CIRCUIT
- SPEED CONTROL SWITCH
- PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures

DIAGNOSTIC TEST
1. SPEED CONTROL SWITCH NO.1 STUCK





Start the engine.
With a scan tool, monitor each switch function for the Speed Control Switches.
Press and release each Speed Control Button.
Is Switch No.1 Stuck?
Yes>> Replace the Speed Control Switch. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4. Powertrain Verification Test - Ver 4
No>> Go To 2

2. SPEED CONTROL SWITCH STATUS





Start the engine.
With a scan tool, monitor each switch function for the Speed Control Switches.
Press and release each Speed Control Button.
- Resume/Accel
- Cancel
- Decel (Coast)
- On/Off
- Set
Does each switch function change status when pressing and releasing each switch?
Yes>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 3

3. SPEED CONTROL SWITCHES
Turn the ignition off.
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 circuit of the Switch when holding the switch button in the following position.
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
The following resistance specs are taken between terminals (V37) S/C Switch No.1 Signal and (V937) S/C Switch Return circuits of the Switch when holding the switch button in the following position
On/Off- 0.47 k ohms
Set- 5.49 k ohms
Coast- 2.94 k ohms
Cancel- 1.24 k ohms
Resume/Accel - 15.4 k ohms
Does the function on the Speed Control Switches have the correct resistance value?
Yes>> Go To 4
No>> Replace the Speed Control Switch that had the incorrect resistance value. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.

4. (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE





Turn the ignition off.
Disconnect the PCM harness connectors.
Ignition on, engine not running.
Measure the voltage of the (V37) S/C Switch No.1 Signal circuit in the S/C Switch harness connector.
Is the voltage above 5.0 volts?
Yes>> Repair the short to voltage in the (V37) S/C Switch No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 5

5. (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE





Measure the voltage of the (V38) S/C Switch No.2 Signal circuit in the S/C Switch harness connector.
Is the voltage above 5.0 volts?
Yes>> Repair the short to voltage in the (V38) S/C Switch No.2 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 6

6. (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT OPEN





Turn the ignition off.

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 (V37) S/C Switch No.1 Signal circuit from both Speed Control harness connectors to the appropriate terminals of special tool # 8815.
Is the resistance below 5.0 ohms for both measurements?
Yes>> Go To 7
No>> Repair the open in the (V37) S/C Switch No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.

7. (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT OPEN





Measure the resistance of the (V38) S/C Switch No.2 Signal circuit from both Speed Control harness connectors to the appropriate terminals of special tool # 8815.
Is the resistance below 5.0 ohms for both measurements?
Yes>> Go To 8
No>> Repair the open in the (V38) S/C Switch No.2 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.

8. (V937) SWITCH RETURN OPEN





Note: The measurement must be taken from both Speed Control Switch harness connectors. Measure the resistance of the (V937) Switch Return circuit from the Speed Control harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms for both measurements?
Yes>> Go To 9
No>> Repair the open in the (V937) Switch Return circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.

9. (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (V37) S/C Switch No.1 Signal circuit in the Speed Control harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the short to ground in the (V37) S/C Switch No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 10

10. (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (V38) S/C Switch No.2 Signal circuit in the Speed Control harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the short to ground in the (V38) S/C Switch No.2 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 11

11. (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO THE (V937) SWITCH RETURN CIRCUIT





Measure the resistance between the (V37) S/C Switch No.1 Signal circuit and the (V937) Switch Return circuit in the Speed Control harness connector.
Is the resistance below 5.0 ohms?
Yes>> Repair the short between the (V937) Switch Return circuit and the (V37) S/C Switch No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 12

12. (V38) S/C SWITCH NO.2 SIGNAL CIRCUIT SHORTED TO THE (V937) SWITCH RETURN CIRCUIT





Measure the resistance between the (V38) S/C Switch No.2 Signal circuit and the (V937) Switch Return circuit in the Speed Control harness connector.
Is the resistance below 5.0 ohms?
Yes>> Repair the short between the (V937) Switch Return circuit and the (V38) S/C Switch No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 13

13. 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 (V37) S/C Switch No.1 Signal circuit and 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 do you less than a 0.2 of a volt difference between the voltmeter switch values and the scan tool switch value?
Yes>> Replace the Speed Control Switch. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 14

14. 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.
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