P0591
P0591-SPEED CONTROL SWITCH 2 PERFORMANCE
- When Monitored:
With the ignition on and battery voltage greater than 10.4 Volts.
- Set Condition:
The Powertrain Control Module (PCM) detects that the Speed Control signal voltage is implausible.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. DIAGNOSTIC TROUBLE CODE (DTC) IS ACTIVE
NOTE: Refer to the following table when diagnosing speed control switch voltage DTCs.
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 both switches simultaneously. Test drive the vehicle and activate the Speed Control system. If the DTC matures to an active fault a repair is necessary.
1. Start the engine and allow it to idle for at least 60 seconds.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
NOTE: It may be necessary to test drive the vehicle and operate the speed control in order for this DTC to set.
2. With a scan tool, select View DTCs.
Is the status Active for this DTC?
Yes
- Go To 2
No
- Perform the CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. Checking for an Intermittent DTC.
2. SPEED CONTROL SWITCH
1. Turn the ignition off.
2. Remove the Speed Control Switch.
3. Turn the ignition on.
4. With a scan tool, read the (V72) S/C Signal 2 voltage.
NOTE: The (V72) S/C Signal 2 voltage should be above 4.8 Volts with the Speed Control Switch removed.
5. Connect a jumper wire between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit in the Speed Control Switch harness connector.
6. With a scan tool, read the (V72) S/C Signal 2 voltage.
NOTE: The (V72) S/C Signal 2 voltage should be below 0.2 of a Volt with the jumper wire in place.
Is the (V72) S/C Signal 2 voltage above 4.8 Volts with the Speed Control Switch removed and below 0.2 of a Volt with the jumper wire in place?
Yes
- Replace the Speed Control Switch.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
No
- Go To 3
3. SPEED CONTROL SWITCH WIRING HARNESS
1. Turn the ignition off.
2. Disconnect the C8 Clockspring harness connector.
3. Turn the ignition on.
4. With a scan tool, read the (V72) S/C Signal 2 voltage.
NOTE: The voltage should be above 4.8 Volts with the C8 Clockspring connector disconnected.
5. Connect a jumper wire between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit at the C8 Clockspring connector, not at the harness connector.
6. With a scan tool, read the (V72) S/C Signal 2 voltage.
NOTE: The (V72) S/C Signal 2 voltage should be below 0.2 of a Volt with the jumper wire in place.
Are the Speed Control voltages displayed as described?
Yes
- Replace the wiring harness between the Speed Control switch and the Clockspring.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
No
- Go To 4
4. CLOCKSPRING
1. Turn the ignition off.
2. Disconnect the C2 Clockspring harness connector.
3. Turn the ignition on.
4. With a scan tool, read the (V72) S/C Signal 2 voltage.
NOTE: The voltage should be above 4.8 Volts with the connector disconnected.
5. Connect a jumper wire between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit in the C2 Clockspring harness connector.
6. With a scan tool, read the (V72) S/C Signal 2 voltage.
NOTE: The (V72) S/C Signal 2 voltage should be below 0.2 of a Volt with the jumper wire in place.
Are the Speed Control voltages displayed as described?
Yes
- Replace the Clockspring.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
No
- Go To 5
5. (V72) S/C SIGNAL 2 CIRCUIT SHORTED TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the Powertrain Control Module (PCM) C3 harness connector.
3. Turn the ignition on.
4. Measure the voltage of the (V72) S/C Signal 2 circuit in the Clockspring C2 harness connector.
Is there any voltage present?
Yes
- Repair the short to voltage in the (V72) S/C Signal 2 circuit.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
No
- Go To 6
6. (V72) S/C SIGNAL 2 CIRCUIT SHORTED TO GROUND
1. Turn the ignition off.
2. Measure the resistance between ground and the (V72) S/C Signal 2 circuit in the Clockspring C2 harness connector.
Is the resistance above 100 Ohms?
Yes
- Go To 7
No
- Repair the short to ground in the (V72) S/C Signal 2 circuit.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
7. (V72) S/C SIGNAL 2 CIRCUIT SHORTED TO THE (V937) S/C SWITCH GROUND CIRCUIT
1. Measure the resistance between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit in the Clockspring C2 harness connector.
Is the resistance above 100 Ohms?
Yes
- Go To 8
No
- Repair the short between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
8. (V72) S/C SIGNAL 2 CIRCUIT OPEN OR HIGH RESISTANCE
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 PCM Pinout Box 8815 to perform diagnosis.
1. Measure the resistance of the (V72) S/C Signal 2 circuit between the Clockspring C2 harness connector and the appropriate terminal of PCM Pinout Box 8815.
Is the resistance below 5.0 Ohms?
Yes
- Go To 9
No
- Repair the open or high resistance in the (V72) S/C Signal 2 circuit.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
9. (V937) S/C SWITCH GROUND CIRCUIT OPEN OR HIGH RESISTANCE
1. Measure the resistance of the (V937) S/C Switch Ground circuit between the Clockspring C2 harness connector and the appropriate terminal of PCM Pinout Box 8815.
Is the resistance below 5.0 Ohms?
Yes
- Go To 10
No
- Repair the open or high resistance in the (V937) S/C Switch Ground circuit.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
10. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Speed Control Switch and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module connectors.
4. Look for broken, bent, pushed out or corroded terminals.
5. Perform any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
No
- Replace the Powertrain Control Module (PCM).
- Perform the PCM VERIFICATION TEST. PCM Verification Test.