P0579-SPEED CONTROL SWITCH 1 PERFORMANCE
For a complete wiring diagram Refer to Section 8W.
- 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. One trip fault.
| Possible Causes |
| (V371) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE |
| (V71) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE |
| (V371) S/C SWITCH NO.1 SIGNAL CIRCUIT OPEN |
| (V71) S/C SWITCH NO.1 SIGNAL CIRCUIT OPEN |
| (V397) SWITCH RETURN CIRCUIT OPEN |
| (V937) SWITCH RETURN CIRCUIT OPEN |
| (V371) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO GROUND |
| (V71) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO GROUND |
| (V371) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO THE (V397) SWITCH RETURN CIRCUIT |
| (V71) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO THE (V937) SWITCH RETURN CIRCUIT |
| STEERING COLUMN CONTROL MODULE |
| SPEED CONTROL SWITCH |
| PCM |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
Diagnostic Test
1. SPEED CONTROL SWITCH STATUSStart 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.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 2
2. SPEED CONTROL SWITCH
Turn the ignition off.
Remove and disconnect the Speed Control Switches from the steering wheel per Service Information.
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 (V371) S/C Switch No.1 Signal and (V397) S/C Switch Return circuits of the Switch when holding the switch button in the following position
Not pressing any switch - 20.5 kohms
On/Off - 0.47 kohms
Set - 5.49 kohms
Coast - 2.94 kohms
Cancel - 1.24 kohms
Resume/Accel - 15.4 kohms
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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
3. (V371) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Disconnect the C3 PCM harness connector.
Disconnect the C3 Steering Column Control Module harness connector.
Ignition on, engine not running.
Measure the voltage on the (V371) S/C Switch No.1 Signal circuit in the S/C Switch harness connectors.
Is the voltage above 0 volts?
Yes
- Repair the short to battery voltage in the (V371) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 4
4. (V71) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Disconnect the C1 Steering Column Control Module harness connector per Service Information.
Ignition on, engine not running.
Measure the voltage on the (V71) S/C Switch No.1 Signal circuit in the C1 SCCM harness connector.
Is the voltage above 0 volts?
Yes
- Repair the short to battery voltage in the (V71) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 5
5. STEERING COLUMN CONTROL MODULE
Turn the ignition off.
Measure the resistance of the (V371), (V71) S/C Switch No.1 Signal circuit between the C1 and C3 SCCM connections.
Measure the resistance of the (V397), (V937) Switch Return circuit between the C1 and C3 SCCM connections.
Is the resistance above 5.0 ohms for either reading?
Yes
- Replace the Steering Column Control Module per Service Information.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 6
6. (V371) S/C SWITCH NO.1 SIGNAL CIRCUIT OPEN
NOTE: The measurement must be taken from both Speed Control Switch harness connectors.
Measure the resistance of the (V371) S/C Switch No.1 Signal circuit from the Speed Control Switches to the C3 SCCM harness connector.
Is the resistance below 5.0 ohms for each measurement?
Yes
- Go To 7
No
- Repair the open in the (V371) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
7. (V71) S/C SWITCH NO.1 SIGNAL CIRCUIT OPEN
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 (V71) S/C Switch No.1 Signal circuit from the C1 SCCM harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms for both measurements?
Yes
- Go To 8
No
- Repair the open in the (V71) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
8. (V397) SWITCH RETURN CIRCUIT OPEN
NOTE: The measurement must be taken from both Speed Control Switch harness connectors.
Measure the resistance of the (V397) Switch Return circuit from the S/C Switch harness connectors to the C3 SCCM harness connector.
Is the resistance below 5.0 ohms for each measurement?
Yes
- Go To 9
No
- Repair the open in the (V397) Switch Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
9. (V937) SWITCH RETURN CIRCUIT OPEN
Measure the resistance of the (V937) Switch Return circuit from the C1 SCCM harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms for both measurements?
Yes
- Go To 10
No
- Repair the open in the (V937) Switch Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
10. (V71) S/C NO.1 SWITCH SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (V71) S/C Switch No.1 Signal circuit in the C1 SCCM harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the short to ground in the (V71) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 11
11. (V371) S/C NO.1 SWITCH SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (V371) S/C Switch No.1 Signal circuit in the S/C Switch harness connectors.
Is the resistance below 100 ohms?
Yes
- Repair the short to ground in the (V371) S/C Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 12
12. (V371) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO THE (V397) S/C SWITCH RETURN CIRCUIT
Measure the resistance between the (V371) S/C Switch No.1 Signal circuit and the (V397) S/C Switch Return circuit in the S/C Switch harness connectors.
Is the resistance below 5.0 ohms?
Yes
- Repair the short between the (V371) S/C Switch No.1 Signal circuit and the (V397) Switch Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 13
13. (V71) S/C SWITCH NO.1 SIGNAL CIRCUIT SHORTED TO THE (V937) S/C SWITCH RETURN CIRCUIT
Measure the resistance between the (V71) S/C Switch No.1 Signal circuit and the (V937) S/C Switch Return circuit in the C1 SCCM harness connector.
Is the resistance below 5.0 ohms?
Yes
- Repair the short between the (V71) S/C Switch No.1 Signal circuit and the (V937) Switch Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 14
14. SPEED CONTROL SWITCH VOLTAGE VALUES
Allow the engine to idle.
With a scan tool, monitor the S/C Switch voltage readings.
| SWITCH POSITION | SWITCH No.1 VOLTAGE VALUE | SWITCH No.2 VOLTAGE VALUE |
| NO SWITCHES PRESSED | 4.31 to 4.78 volts | 4.31 to 4.78 volts |
| ON/OFF PRESSED | 0.59 to 1.13 volts | 3.53 to 3.92 volts |
| RES/ACCEL PRESSED | 3.88 to 4.17 volts | 2.04 to 2.47 volts |
| SET PRESSED | 3.16 to 3.56 volts | 1.17 to 1.56 volts |
| COAST PRESSED | 2.57 to 2.94 volts | 0.77 to 1.09 volts |
| CANCEL PRESSED | 1.59 to 1.99 volts | 2.84 to 3.25 volts |
Take these same voltage measurements with a voltmeter by back probing the (V371) S/C Switch No.1 Signal circuit and the (V372) 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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 15
15. 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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Replace and program the Powertrain Control Module per Service Information.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)