NGC

P0591-SPEED CONTROL SWITCH 2 PERFORMANCE

For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
With the ignition on and battery voltage greater than 10.4 volts.

- Set Condition:
The PCM detects that the Speed Control signal voltage is implausible.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. 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.

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 can result in personal injury or death.

NOTE: It may be necessary to test drive the vehicle and operate the speed control in order for this DTC to set.

With a scan tool, select View DTCs.
Is the status Active for this DTC?

Yes

- Go to 2

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC

2. SPEED CONTROL SWITCH




Turn the ignition off.
Remove the Speed Control Switch.
Turn the ignition on.
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.

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.
With a scan tool, read the (V72) S/C Signal 2 voltage.

NOTE: The (V72) S/C Signal 2 voltage should be below.2 volts 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.2 volts with the jumper wire in place?

Yes

- Replace the Speed Control Switch.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 3

3. CLOCKSPRING
Turn the ignition off.
Disconnect the C5 Steering Control Module (SCM) harness connector.
Turn the ignition on.
With a scan tool, read the (V72) S/C Signal 2 voltage.

NOTE: The voltage should be above 4.8 volts with the C5 Steering Control Module (SCM) connector disconnected.

Connect a jumper wire between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit at the C5 Steering Control Module (SCM) connector, not at the harness connector.
With a scan tool, read the (V72) S/C Signal 2 voltage.

NOTE: The (V72) S/C Signal 2 voltage should be below.2 volts with the jumper wire in place.

Are the Speed Control voltages displayed as described?

Yes

- Replace the Clockspring.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 4

4. STEERING CONTROL MODULE (SCM)




Turn the ignition off.
Disconnect the C2 Steering Control Module (SCM) harness connector.
Turn the ignition on.
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.

Connect a jumper wire between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit in the C2 Steering Control Module (SCM) harness connector.
With a scan tool, read the (V72) S/C Signal 2 voltage.

NOTE: The (V72) S/C Signal 2 voltage should be below.2 volts with the jumper wire in place.

Are the Speed Control voltages displayed as described?

Yes

- Replace the Steering Control Module (SCM).
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 5

5. (V72) S/C SIGNAL 2 CIRCUIT SHORTED TO VOLTAGE




Turn the ignition off.
Disconnect the C3 Powertrain Control Module (PCM) harness connector.
Turn the ignition on.
Measure the voltage of the (V72) S/C Signal 2 circuit in the C2 Steering Control Module (SCM) 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. Powertrain Verification Test

No

- Go to 6

6. (V72) S/C SIGNAL 2 CIRCUIT SHORTED TO GROUND




Turn the ignition off.
Measure the resistance between ground and the (V72) S/C Signal 2 circuit in the C2 Steering Control Module (SCM) 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. Powertrain Verification Test

7. (V72) S/C SIGNAL 2 CIRCUIT SHORTED TO THE (V937) S/C SWITCH GROUND CIRCUIT




Measure the resistance between the (V72) S/C Signal 2 circuit and the (V937) S/C Switch Ground circuit in the C2 Steering Control Module (SCM) 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.Powertrain 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 Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (V72) S/C Signal 2 circuit between the S/C Switch harness connector and the appropriate terminal of special tool #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. Powertrain Verification Test

9. (V937) S/C SWITCH GROUND CIRCUIT OPEN OR HIGH RESISTANCE




Measure the resistance of the (V937) S/C Switch Ground circuit between the S/C Switch harness connector and the appropriate terminal of special tool #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. Powertrain Verification Test

10. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Speed Control Switch and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module connectors.
Look for broken, bent, pushed out or corroded terminals.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Replace the Powertrain Control Module (PCM).
- Perform the PCM Verification Test. Powertrain Verification Test