P0579
P0579-SPEED CONTROL SWITCH 1 PERFORMANCE (ETC)
For a complete wiring diagram refer to Diagrams/Electrical.
- When Monitored:
With the ignition key on.
- Set Condition:
Cruise switch voltage output is not out of range but it does not equal any of the values for any of the button positions.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. SPEED CONTROL SWITCH STATUS
Start the engine.
With a scan tool, monitor each which function for the Speed Control Switches.
Notice the voltage reading when no buttons are pressed.
Press and release each Speed Control Button.
- Resume/Accel
- Cancel
- Decel (Coast)
- On/Off
- Set
Does each switch function change status when pressing and then depressing each switch?
Yes
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 2
2. SPEED CONTROL SWITCH
Turn the ignition off.
Remove and disconnect 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 (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
Not pressing any switch - 20.5k ohms
On/Off - 0.47k ohms
Set - 5.49k ohms
Coast - 2.94k ohms
Cancel - 1.24k ohms
Resume/Accel - 15.4k 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 the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
3. (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Disconnect the C3 PCM harness connector.
Ignition on, engine not running.
Measure the voltage on the (V37) S/C Switch No.1 Signal circuit in the Speed Control harness connector.
Is the voltage above 5.0 volts?
Yes
- Repair the short to battery voltage in the (V37) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 4
4. CLOCKSPRING
Turn the ignition off.
Disconnect the upper and lower clockspring harness connectors.
Measure the resistance of the (V37) S/C Switch No.1 Signal circuit between the upper and lower clockspring harness connectors.
Measure the resistance of the (V937) Switch Return circuit between the upper and lower clockspring harness connectors.
Is the resistance above 5.0 ohms?
Yes
- Replace the Clockspring.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 5
NOTE: Connect the Clockspring harness connectors before continuing.
5. (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT OPEN
NOTE: The measurement must be taken from both Speed Control Switch harness connectors.
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 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 6
No
- Repair the open in the (V37) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
6. (V937) SWITCH RETURN CIRCUIT 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 7
No
- Repair the open in the (V937) Switch Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
7. (V37) S/C NO.1 SWITCH 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 the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 8
8. (V37) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO THE (V937) S/C SWITCH RETURN CIRCUIT
Measure the resistance between the (V37) S/C Switch No.1 Signal circuit and the (V937) S/C Switch Return circuit in the Speed Control harness connector.
Is the resistance below 5.0 ohms?
Yes
- Repair the short between the (V37) S/C Switch No.1 Signal circuit and the (V937) Switch Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 9
9. SPEED CONTROL SWITCH VOLTAGE VALUES
Connect the C3 PCM harness connector and the S/C Switch harness connectors.
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 is there 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 the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
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 the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test