P0805
PowertrainClutch Position Sensor Circuit
The ECU has spotted a voltage or resistance reading from the clutch pedal position sensor that's outside the range it expects on a manual car. That sensor tells the car where the clutch pedal is, and the system uses it for the start interlock and on some cars for shift logic. For most owners this shows up as a warning light and, on the more annoying examples, a car that either won't crank with the clutch flat to the floor or one that happily starts without you touching the clutch at all.
ⓘ Information only. This page provides general educational information about fault code P0805. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0805 mean?
P0805 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Clutch Position Sensor Circuit.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine or transmission warning light on the dash, sometimes the only thing you'll notice
- • Engine cranks and starts without the clutch pedal pressed, which is a genuine safety issue on cars with keyless or remote start
- • Occasionally the opposite problem: it refuses to crank even with the clutch fully down
- • Odd idle behaviour or a flare in revs as you press or release the clutch
- • On some cars the gearbox drops into limp mode or gets fussy about selecting gears
- • Plenty of vehicles show nothing wrong to drive apart from the light
Possible causes
Causes commonly associated with P0805, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Faulty or knocked-out-of-position clutch pedal switch. These are mounted up under the dash near the pedal box and take a beating from feet over the years
- 2. Corroded or loose connector at the sensor, very common on cars that have had footwell damp or a leaking screen washer line
- 3. Switch out of adjustment so it isn't making proper contact when the pedal moves, often after clutch work or pedal box disturbance
- 4. Wiring fault between the switch and the ECU, either a chafed wire gone to ground or a broken core
- 5. Blown fuse or failed feed on the switch supply circuit
- 6. A duff ECU or a software calibration glitch, but this is rare and the last thing to suspect
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Pull every stored and pending code first. P0805 sitting alongside body or start-system codes points you straight at the interlock circuit rather than the gearbox itself
- 2. Get up under the dash to the clutch switch, give it a wiggle and check it's clipped in and aligned. A switch that's drooped off its bracket will throw this code and is a two-minute fix
- 3. Unplug the connector and look for green corrosion, spread pins or a loose terminal, clean it up and reseat it before you go any further
- 4. With the multimeter, check you've got the proper supply voltage at the switch with the ignition on, usually a 5V reference or battery feed depending on the car
- 5. Press the pedal and watch the output change as the switch operates. No change means a dead switch
- 6. If supply, signal and connections all check out, go through the wiring back to the ECU for an open or a short, then and only then start thinking about the module
Common questions about P0805
Can I keep driving it like this? +
Depends which way the fault has gone. If your car now starts without the clutch pressed, treat that seriously, especially if it's in gear or you've got keyless start, because it can lurch forward when you turn the key. If it's just a warning light and the car drives and starts normally, it's not going to leave you stranded, but get the switch looked at soon rather than living with it for months.
Is this going to be an MOT problem? +
The clutch position switch isn't a tested item in itself, the tester checks the physical condition of the clutch and gearbox, not the electronics. The catch is the warning light. If the engine or transmission lamp is lit at the time of test the tester can pull you up on it, so clear the fault and let the light go out before you book the car in.
What's this likely to cost me? +
If it's just the switch, you're looking at a cheap part and an hour or so of labour, so often under £100 at a decent independent. Add wiring repair and that climbs into the low hundreds because tracing a fault takes time. A main dealer will charge more on labour and want a genuine part, so the same job can be half again as much. ECU work is the worst case and uncommon.
How do I tell whether it's the switch or the wiring on my car? +
Start at the switch and work outward. Wiggle the connector and operate the pedal while watching live data or a meter on the signal wire. If the reading jumps about when you flex the loom, you've got a wiring or connector fault. If the signal simply never changes when the pedal moves and the supply voltage is present, the switch itself is dead. A switch that's physically hanging loose or out of adjustment usually fixes the lot once it's reseated.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →