P1593
P1593-SPEED CONTROL SWITCH 1/2 STUCK
For a complete wiring diagram refer to Diagrams/Electrical.
- When Monitored:
Ignition on.
- Set Condition:
Cruise Switch inputs are not coherent with each other. Example: PCM is reading Switch No.1 as Accel and Switch No.2 as Coast at the same time. One trip fault.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
Ignition on, engine not running.
NOTE: This DTC is a two trip fault. If the scan tool indicates a one trip failure, the possible cause may have been the customer pressing the switch in two positions simultaneously. Test drive the vehicle and activate the Speed Control system. If the DTC matures to an active fault a repair is necessary.
Ask the customer if it is possible that button was held in two positions at the same time before this DTC set. If this is the case, no repair is necessary.
Start the engine.
Allow the engine to reach normal operating temperature.
With a scan tool, select View DTCs.
NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
Is the DTC Active or Pending at this time?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
2. SPEED CONTROL SWITCH
With the scan tool, monitor the Speed Control Switch voltage.
Disconnect the Speed Control Switch harness connector.
Did the voltage change to above 4.8 volts?
Yes
- Replace the Speed Control Switch.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 3
3. SPEED CONTROL SWITCHES
Turn the ignition off.
Remove and disconnect the Speed Control Switch 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 (V72) S/C Signal 2 and (V937) S/C Return circuits of the Switch when holding the switch button in the following position.
Not pressing any switch - 20.5 kohms
On/Off - 8.87 kohms
Set - 0.825 kohms
Coast - 0.47 kohms
Cancel - 3.92 kohms
Resume/Accel - 1.87 kohms
The following resistance specs are taken between terminals (V71) S/C Signal 1 and (V937) S/C 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 Switch have the correct resistance value?
Yes
- Go To 4
No
- Replace the Speed Control Switch that had the incorrect resistance value.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
4. S/C SWITCH SIGNAL CIRCUIT SHORTED TO VOLTAGE
Disconnect the C3 PCM harness connector.
Measure the voltage on the (V71) and (V72) S/C Signal circuits at the Speed Control harness connector.
Is there any voltage present?
Yes
- Repair the short to voltage in the (V71) or (V72) S/C Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 5
5. S/C SWITCH 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.
Turn the ignition off.
Measure the resistance of the (V71) and (V72) S/C Signal circuits from both Speed Control harness connector to the appropriate terminals of special tool #8815.
Is the resistance below 5.0 ohms for each measurement?
Yes
- Go To 6
No
- Repair the excessive resistance in the (V71) or (V72) S/C 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) S/C Return circuit at 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 excessive resistance in the (V937) S/C Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
7. S/C SWITCH SIGNAL CIRCUITS SHORTED TO THE (V937) S/C RETURN CIRCUIT
Measure the resistance between the (V937) S/C Return circuit and both of the (V71) and (V72) S/C Signal circuits in the S/C Switch harness connector.
Is the resistance below 5.0 ohms?
Yes
- Repair the short between the (V937) S/C Return circuit and the (V71) or (V72) S/C Switch Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 8
8. (V71) S/C SIGNAL 1 CIRCUIT SHORTED TO THE (V72) S/C SIGNAL 2 CIRCUIT
Measure the resistance between the (V71) S/C Signal 1 circuit and the (V72) S/C Signal 2 circuit at the Speed Control harness connector.
Is the resistance below 100 ohms for each circuit?
Yes
- Repair the short between the (V72) S/C Signal 2 circuit and the (V71) S/C Signal 1 circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 9
9. S/C SWITCH SIGNAL CIRCUITS SHORTED TO GROUND
Measure the resistance between ground and the (V71) and (V72) S/C Switch Signal circuits at both S/C Switch harness connectors.
Is the resistance below 100 ohms?
Yes
- Repair the short to ground in the (V71) or (V72) S/C Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 10
10. 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 (V71) S/C Signal 1 circuit and the (V72) S/C Signal 2 circuit at the switch.
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 the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 11
11. 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