Cruise Control Multi-Function Input Circuit Range/Performance
The P0579 code indicates that the Powertrain Control Module (PCM) has detected an abnormal voltage signal from the cruise control multi-function switch. This switch combines functions like set, resume, cancel, and coast into a single input circuit. The PCM monitors the voltage to determine which button is pressed. A range/performance issue means the signal is outside expected parameters, often due to a faulty switch, wiring issues, or a poor ground.
1. Most Common Causes
- Faulty cruise control multi-function switch
- Damaged or corroded wiring/connectors in the cruise control circuit
- Poor ground connection
- Faulty PCM (rare)
2. Symptoms You Will Notice
- Cruise control inoperative
- Cruise control light on dash stays on or flashes
- Cruise control engages but does not respond to buttons
- Engine light illuminated
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for other related codes.
Step 2: Visually inspect the cruise control switch and wiring for damage or corrosion.
Step 3: Test the switch resistance with a multimeter and compare to manufacturer specs.
Step 4: Check the voltage signal at the PCM connector with the switch pressed.
Step 5: If all checks pass, suspect a PCM issue and perform a relearn or replacement.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, it is generally safe to drive, but cruise control will not function properly. The vehicle's braking and acceleration are unaffected.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and switch replacement. Labor is about $50-$100, and the switch costs $20-$50.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.