DTC P0581: Speed Control Switch #1 High: Testing

Do not press any of the Speed Control Switch buttons. Turn ignition on, engine not running. With the DRBIII®, monitor the Speed Control voltage. Is the Speed Control voltage above 4.8 volts? If yes, go to next step. If no, go to step 5.

Turn the ignition off. Remove the Speed Control Switches from the steering wheel. Measure the resistance across each Speed Control Switch. Monitor the ohmmeter while pressing each function button on each switch. Does the Speed Control Switches have the correct resistance values? See SPEED CONTROL SWITCH RESISTANCE table. If yes, go to next step. If no, replace the Speed Control Switch that had the incorrect resistance value.

SPEED CONTROL SWITCH RESISTANCE

Switch	Ohms
Cancel	900-918
Decel (Coast)	2910-2970
On/Off	0
Resume/Accel	15,400
Set	6584-6716

Ensure the ignition is off. Disconnect the PCM harness connector. Measure the voltage of the Speed Control Switch Signal circuit at one of the Speed Control Switch harness connectors. Is the voltage above 5.0 volts? If yes, repair the short to battery voltage in the Speed Control Switch Signal circuit. If no, go to next step.

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. Use Miller Special Tool (8815) when performing diagnosis at PCM harness connectors.

Measure the resistance of the Sensor Ground circuit from the Speed Control Switch harness connector to the appropriate terminal of the Miller Special Tool. Measure resistance at both Speed Control Switch harness connectors. Is the resistance below 5.0 ohms for both measurements? If yes, check the PCM harness connector terminals for corrosion, damage or terminal push out. Repair as necessary. If connectors are okay, replace PCM. Program the new PCM. See PROGRAMMING . If no, repair the open in the Sensor Ground circuit.

WARNING: When the engine is operating, do not stand in a direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing.

The conditions that set the DTC are not present at this time. The following may help in identifying the intermittent condition. With the engine running at normal operating temperature, monitor the DRBIII® parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a DTC to set. Review the DRBIII® Freeze Frame information. If possible, try to duplicate the conditions under which the DTC was set. Refer to any Technical Service Bulletins (TSB) that may apply. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals. Were any of the above conditions present? If yes, repair as necessary. If no, test is complete.