P0579, P0591 Speed Control Switch (1 and 2) Performance

P0579 Speed Control Switch 1 Performance
P0591 Speed Control Switch 2 Performance

P0579, P0591 Code - the Speed Control Switch are located in the right steering wheel switch. The speed control switch is a redundant switch consisting of two 5 volt signals sharing a common return circuit.

The right steering wheel switch is hard wired to the Powertrain Control Module (PCM) via the clockspring pass-through within the steering column control module (SCCM). The SCCM is located near the top of the steering column below the steering wheel. The SCCM includes the steering column shroud, the steering angle sensor (SAS), the clockspring, the Multi-function switch, a steering column power tilt and telescope switch (if equipped), and a trim cover. Set condition, the Powertrain Control Module (PCM) has detected that a non-permissable combination has occured in the speed control switch.

Possible causes P0579, P0591 Code

• Resistance in the S/C signal circuit
• Speed control switch (RIight steering wheel switch)
• Clockspring

Diagnose P0579, P0591 Code

Step 1. Check for active DTCs

Test drive the vehicle and operate and operate all of the speed control switch positions. With the scan tool, read DTCs.

Does the scan tool display this DTC as active?

Yes, go to step 2.

No, perform the PCM intermittent condition.

Step 2. Check the S/C Signal circuit

Turn the ignition off. Turn the ignition off disconnect the 12-volt battery wait two minutes before proceeding. Failure to follow these instructions may result in possible serious or fatal injury. Remove the Driver Airbag. Do not place an intact non-deployed airbag face down on a hard surface, the airbag propels into the air if accidentially deployed. Failure to follow these instructions mat result on possible serious or fatal injury. Back probe the S/C signal circuit at the right steering wheel switch harness connector. Turn th ignition on, measure the voltage on the S/C signal circuit at the steering wheel switch harness connector.

Is the voltage between 4.9 and 5.1 volts?

Yes, check for speed terminals at the connector. If the connector and terminals are good, replace the right steering wheel switch. If the P0579 and P0591 Codes are both present simultaneously, the most likely cause is resistance in the S/C switch ground circuit which is shared by both sensors. If both faults are present, check the sensor ground for high resistance before replacing the switch.

No, go to step 3.

Step 3. Check the S/C signal circuit for an open/high resistance

Turn the ignition off, disconnect the right steering wheel switch harness connector. Disconnect the PCM harness connector, measure the resistance of the S/C signal circuit between the steering wheel switch harness connector and the PCM harness connector.

Is the resistance below 2.0 Ohms?

Yes, replace and program the Powertrain Control Module (PCM). Perform the Powertrain verification test.

No, go to step 4.

Step 4. Check the Steering Wheel harness

Disconnect and remove wheel switch harness from the steering wheel switch and SCM. Measure the resistance of the S/C signal circuit in the steering wheel switch harness.

Is the resistance below 2.0 Ohms?

Yes, go to step 5.

No, replace the steering wheel harness.

Step 5. Check the Clocksping/steering control Module

Disconnect the steering control module harness connector. Measure the resistance of the S/C signal circuit between the steering control module and the PCM harness connector.

Is the resistance below 2.0 Ohms?

Yes, replace the steering control module.

No, repair the S/C signal circuit for an open or high resistance.

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