Cruise Control Multi-Function Input Circuit Range/Performance
The P0591 code indicates that the Powertrain Control Module (PCM) has detected an abnormal voltage or signal from the cruise control multi-function switch circuit. This switch typically controls functions like set, resume, cancel, and coast. The issue is often due to a faulty switch, wiring problems, or a malfunctioning PCM.
01. Most Common Causes
- Faulty cruise control multi-function switch
- Damaged or corroded wiring/connectors in the switch circuit
- Blown fuse related to cruise control
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Cruise control inoperative
- Cruise control light on dash flashing or staying on
- Engine Check Light illuminated
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm 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's resistance or voltage with a multimeter according to manufacturer specs.
Step 4: Check the cruise control fuse and replace if blown.
Step 5: If all else fails, test the PCM for proper operation (requires advanced diagnostics).
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, it is generally safe to drive, but cruise control will not function. The vehicle's braking and acceleration are unaffected.
How much does it cost to fix?▼
Typically between $50 and $150 for diagnosis and replacement of the switch, though costs can vary based on labor rates and parts.