P1800 Code: Transmission Clutch Interlock Safety Switch Circuit Failure
🟠 Moderate severity · drivable
The car may not start or may start without pressing the clutch, but once running you can drive.
What P1800 means
The clutch interlock safety switch circuit has failed. This switch keeps the engine from starting unless the clutch pedal is pressed, and when the circuit fails the engine computer stores P1800. Depending on how it fails, the car may refuse to start or may start without the clutch pressed.
Symptoms
- Check engine light is on
- Engine won't crank or start
- Engine starts without pressing the clutch
- Intermittent starting problems
Common causes
- most common: Faulty clutch interlock switch
- common: Misadjusted switch
- common: Damaged wiring or connector
- less common: Blown fuse
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the clutch interlock switch | Yes | $30–120 |
| Adjust the switch position | Yes | $0–50 |
| Repair wiring or replace the fuse | Yes | $10–60 |
Frequently asked questions
Can I drive with a P1800 code?
Once the engine is running, yes. The main risk is the car not starting or starting without the clutch pressed, so fix it soon.
Why won't my car start with a P1800?
The clutch interlock switch or its circuit is failing, so the computer may not get the signal that the clutch is pressed and blocks the starter.
How much does it cost to fix a P1800?
Most repairs cost $30–$120 for a new switch, plus a little more if wiring or a fuse also needs attention.
Related codes
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.