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P0591







P0591-SPEED CONTROL SWITCH 2 PERFORMANCE





For a complete wiring diagram Consult 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. One trip fault.





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

Diagnostic Test

1. ACTIVE DTC
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.
Allow the engine to reach normal operating temperature.

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.

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 SWITCHES
Turn the ignition off.
Remove the Speed Control Switch from the steering wheel.
Measure the resistance across the Speed Control Switch.
Monitor the ohmmeter while pressing each function button on the switch.
The following resistance specs are taken between terminals (V72) S/C Signal 2 circuit and (V937) S/C Return circuit of the Switch when holding the switch button in the following position.
Not pressing any switch - 20.5k ohms
On/Off - 8.87k ohms
Set - 0.825k ohms
Coast - 0.47k ohms
Cancel - 3.92k ohms
Resume/Accel - 1.87k ohms
The following resistance specs are taken between terminals (V71) S/C Signal 1 and (V937) S/C Return circuit 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 Switch 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. (V72) S/C SIGNAL 2 CIRCUIT SHORTED TO VOLTAGE




Disconnect the C3 PCM harness connector.
Ignition on, engine not running.
Measure the voltage on the (V72) S/C Signal 2 circuit in the Switch harness connector.
Is there any voltage present?

Yes

- Repair the short to voltage in the (V72) S/C Signal 2 circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go to 4

4. (V72) S/C SIGNAL 2 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 (V72) S/C Signal 2 circuit from the Switch harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?

Yes

- Go to 5

No

- Repair the open in the (V72) S/C Signal 2 circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. (V937) S/C RETURN CIRCUIT OPEN




Measure the resistance of the (V937) S/C Return circuit from the Switch harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?

Yes

- Go to 6

No

- Repair the open in the (V937) S/C Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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




Measure the resistance between ground and the (V72) S/C Signal 2 circuit in the Switch harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (V72) S/C Signal 2 circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go to 7

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




Measure the resistance between the (V72) S/C Signal 2 circuit and the (V937) S/C Return circuit in the Switch harness connector.
Is the resistance below 5.0 ohms?

Yes

- Repair the short between the (V72) S/C Signal 2 circuit and the (V937) S/C Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go to 8

8. SPEED CONTROL SWITCH VOLTAGE VALUES
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 and #8815-1 to perform diagnosis.

Install Miller Special Tool #8815-1 on the C3 PCM harness connector.
Connect the S/C Switch harness connectors.
Connect the SCCM harness connectors.
Turn the ignition on.
With a scan tool, monitor the S/C Switch voltage readings.
Using a voltmeter check the voltage on the (V37) S/C Signal 1 circuit and the (V38) S/C Signal 2 circuit at the appropriate terminals of the special tool #8815.
Monitor the voltmeter.
With a scan tool, monitor the S/C Switch voltage readings.





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

- Verify that there is good pin to terminal contact in the Switches and Powertrain Control Module connectors. Replace the Speed Control Switch if no problems were found in the connectors.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go to 9

9. 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.
Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module connectors.
Search for any Technical Service Bulletins that may apply.
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.

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