Cruise Control Multi-Function Input B Circuit Range/Performance
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.
Can I keep driving? Drivable — the engine runs normally; only cruise control is affected, so there's no urgency beyond restoring cruise.
Real-world scan data
Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.
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?+
Can I just clear P0591?+
Related codes
Read & clear P0591 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.