P0594
Cruise Control Servo Control Circuit/Open
Vehicle speed & idle control
Generic OBD-II
Low
What it means
P0594 means the module detected an open circuit in the cruise control servo control — the actuator that adjusts throttle to hold your set speed. It's a comfort-feature fault: cruise control won't engage or hold speed, but the engine and drivability are unaffected. The usual causes are broken wiring, a bad connector, or a failed servo.
Low
Can I keep driving? Safe to drive — only the cruise control is affected; the engine runs and drives normally.
Common symptoms
What you'll notice
- Cruise control won't engage or won't hold a set speed
- Cruise indicator light may not come on
- Check-engine light on
Common causes
Most likely first
- Open circuit in the cruise control servo wiringLikely
- Failed cruise control servo/actuatorCommon
- Corroded or disconnected connector at the servoCommon
- Faulty cruise control switch or moduleLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame, then check the servo control circuit for an open — inspect the connector and back-probe for continuity.
- Measure the servo winding resistance and compare to spec; an open winding confirms a failed servo.
- Repair broken wiring or corroded pins in the servo circuit.
- Replace the servo if it's internally open. Clear and re-test cruise operation.
FAQ
Quick answers
Is it safe to drive with P0594?+
Yes. The engine and brakes are unaffected — only cruise control won't work until the servo circuit is repaired.
Can I just clear P0594?+
It clears, but an open circuit returns as soon as the module checks the servo. Repair the wiring or servo first.
Related codes
Often seen with P0594
Read & clear P0594 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