Cruise control buttons form a resistor ladder on one or two signal lines, each button giving its own voltage window. FCA uses two lines with offset windows – signal 1 is input A, signal 2 input B – and both must report the same button; GM evaluates the ratio to the reference. Any fault locks out cruise control; CARB treats this as emission-neutral, and GM and Ford set these codes without warning lamp. P0591 means signal 2 is outside its window while a button is pressed – for on/off FCA expects 0.900 V and sets the code above 0.980 V, active only while the button is held. Usual cause is oxidation at the six-pin steering wheel connector; in the Jeep Wrangler JK recalls it indicates a faulty clockspring. GM does not use P0591.
Low severity. Can I keep driving?You can keep driving, but check that the brake lights work: that part is a safety issue.
Symptoms
- Cruise control working sporadically or not at all
- Cruise control locked out
- No check engine light
Most likely causes
- Oxidised steering wheel connector at clockspring or column module
- Clockspring dirty or faulty
- Button block aged
- Column module or PCM
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of P0591 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 5: Speed and idle
- 91: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0591?
You can keep driving, but check that the brake lights work: that part is a safety issue.
What causes code P0591?
The most common causes are: oxidised steering wheel connector at clockspring or column module; clockspring dirty or faulty; button block aged.
Related codes
- P0579Cruise Control Multi-Function Input A Circuit Range/Performance
- P0589Cruise Control Multi-Function Input B Circuit
- P0590Cruise Control Multi-Function Input B Circuit Stuck
- P0592Cruise Control Multi-Function Input B Circuit Low
- P0593Cruise Control Multi-Function Input B Circuit High
- P0585Cruise Control Multi-Function Input A/B Correlation
Sources
- static.nhtsa.gov: MC 10174168 9999
- static.nhtsa.gov: RCRIT 16V290 9641
- static.nhtsa.gov: RCRIT 16V288 5957
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.