P0704
PowertrainClutch Switch Input Circuit Malfunction
The car's computer isn't getting a clean signal from the switch that tells it when you've pushed the clutch pedal down. On most manuals this is the little switch tucked up behind the clutch pedal, and the engine uses it to decide whether it's safe to crank the starter. When the signal goes flaky, you'll usually find the car either won't start at all unless you jiggle things, or it starts without you touching the clutch when it shouldn't. Cruise control often packs in at the same time because it relies on the same switch to drop out when you dip the clutch.
ⓘ Information only. This page provides general educational information about fault code P0704. 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 P0704 mean?
P0704 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Clutch Switch Input Circuit Malfunction.
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 won't crank even with the clutch pedal fully pressed, or only cranks after a few tries
- • Car starts without pressing the clutch when it should require it
- • Cruise control either won't engage or won't cancel when you press the clutch
- • Engine warning light on the dash
- • Intermittent no-start that comes and goes, often worse in cold or damp weather
- • On cars with hill-hold or stop-start, those functions drop out
Possible causes
Causes commonly associated with P0704, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Failed or worn clutch pedal switch, the usual suspect. These are cheap plastic switches that take a hammering every gearchange and eventually stop reading reliably
- 2. Switch knocked out of adjustment so it no longer makes proper contact when the pedal moves. Common after footwell work or a heavy-footed driver
- 3. Corroded or loose connector at the switch, footwells get damp and the pins suffer for it
- 4. Broken or chafed wiring in the loom running up to the pedal box
- 5. Worn clutch pedal bush or pivot letting the pedal sit slightly off, so the switch never quite closes
- 6. Blown fuse on the circuit, less common but quick to rule out
- 7. PCM or software fault, which is rare and the last thing you should 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. Read the codes and watch the clutch switch live data on a scan tool while a helper presses and releases the pedal. The reading should flip cleanly between pressed and released. If it sticks or jumps about, you've found your fault
- 2. Get under the dash and check the switch is actually being contacted by the pedal at the right point. Loose mountings and bent brackets are common, and a tweak of the adjustment fixes a fair few of these
- 3. Unplug the connector at the switch and look for green corrosion, bent pins or oil contamination from a leaking clutch master cylinder
- 4. Test the switch with a multimeter set to continuity, it should change state as you operate it by hand. A switch that reads the same in both positions is dead
- 5. Back-probe the wiring and check you've got voltage at the switch with the ignition on, then trace the circuit for breaks if the voltage is missing
- 6. If the switch, wiring and voltage all check out and the code keeps coming back, only then start looking at the PCM
Common questions about P0704
Can I sort the switch out myself in the driveway? +
For a lot of these, yes. The switch lives behind the clutch pedal and clips or screws in, parts are usually £15 to £40, and adjustment is often just slackening a locknut and repositioning it. The awkward bit is the access. You'll be on your back in the footwell with a torch and not much room. Confirm the fix with a scan tool afterwards, because a switch that reads fine by hand can still misbehave under the car's own voltage.
If I just clear the code, will it stay gone? +
If the switch is worn or out of adjustment, clearing the code buys you a day or two at most before it returns. The fault is mechanical or electrical, so resetting the ECU does nothing to the actual switch. The only time clearing it sticks is if you've already fixed a loose connector or readjusted the switch and you're confirming the repair worked.
What's the risk if I leave it and keep driving? +
The headline danger is a car that cranks without the clutch pressed. Leave it in gear, turn the key out of habit, and it can lurch forward into whatever's in front of you. Beyond that you lose cruise control and on some cars the stop-start and hill-hold. It won't damage the engine or gearbox, but a no-start that strands you at the worst moment, or a car that jumps when you least expect it, is reason enough to deal with it.
How quickly do I need to get this fixed? +
It's not a roadside emergency, but I wouldn't sit on it. The unpredictable starting is the main issue, both the days it won't crank at all and the days it cranks when it shouldn't. Most owners get a week or two of warning before it goes fully intermittent, so book it in soon rather than waiting for it to leave you stuck on a cold morning.
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 →