P0591
Cruise Control Multi-Function Input B Circuit Range/Performance
Cruise control
Generic OBD-II
Low
What it means
P0591 means the "B" signal from the cruise control multi-function switch is out of its expected range, so the ECM can't trust the cruise commands. It's typically a faulty switch or its wiring. Only the cruise control system is affected — the car otherwise drives normally — making this a low-urgency repair.
Low
Can I keep driving? Drivable — the engine runs normally; only cruise control is affected, so there's no urgency beyond restoring cruise.
Common symptoms
What you'll notice
- Cruise control won't set or hold speed
- Cruise control switches unresponsive or erratic
- Check-engine light on
Common causes
Most likely first
- Faulty cruise control multi-function switch B (out-of-range signal)Likely
- Corroded or damaged wiring/connector in the switch circuitCommon
- Poor connection at the switch or steering-wheel clockspringCommon
- Faulty cruise control or powertrain control module (PCM), rareLess often
How to diagnose & fix
Work through it in order
- Confirm only cruise is affected, then inspect the cruise switch and connector.
- Measure the input-B signal — a value outside the expected range points to the switch or its wiring.
- Check the harness and clockspring for damage or intermittent contact.
- Replace the cruise control switch if it tests out of range.
- Clear the code and confirm cruise works on a road test.
FAQ
Quick answers
Is it safe to drive with P0591?+
Yes. This affects only the cruise control system; the engine, brakes, and transmission are unaffected.
Can I just clear P0591?+
It will come back while the switch signal stays out of range. Repairing the switch or wiring is what clears it for good.
Related codes
Often seen with P0591
Read & clear P0591 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX