Cruise Control Multi-Function Input B Circuit High
What it means
P0593 means the PCM sees the cruise-control multi-function switch input "B" reading high (a short to voltage or a switch/wiring fault). This input carries your cruise button presses, so the practical effect is that cruise control won't set or respond. It's a low-severity signalling fault — the engine and brakes are unaffected.
Can I keep driving? Safe to drive — only the cruise-control switch input is affected; the engine runs normally.
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
- Check-engine light on
Common causes
Most likely first
- Failed cruise-control multi-function switch BLikely
- Short to voltage on the switch input circuitCommon
- Corroded or damaged connector or wiringCommon
- PCM/cruise module fault (rare)Less often
How to diagnose & fix
Work through it in order
- Inspect the cruise multi-function switch connector and wiring for a short to voltage or corrosion.
- With a scan tool, watch the switch input while pressing each cruise button; a signal stuck high confirms the fault.
- Replace the cruise-control multi-function switch if it doesn't read correctly.
- Repair any wiring faults, then clear and re-test the cruise control.
FAQ
Quick answers
Is it safe to drive with P0593?+
Can I just clear P0593?+
Related codes
Read & clear P0593 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.