P0320
PowertrainIgnition/Distributor Engine Speed Input Circuit
The ECU watches the pulse signal coming from the crank or cam position sensor every time the engine turns over, and uses it to know exactly where the pistons are so it can time the spark and fuel correctly. When that signal goes ragged, drops out, or disappears entirely, the ECU has no reliable way to fire the cylinders and it logs P0320. For you as the driver this usually shows up as an engine that runs rough, cuts out, or refuses to start, because the brain has temporarily lost track of where everything is.
ⓘ Information only. This page provides general educational information about fault code P0320. 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 P0320 mean?
P0320 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Ignition/Distributor Engine Speed Input 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 warning light on, sometimes with the rev counter twitching or dropping to zero while driving
- • Engine cranks over fine but won't fire up, or stalls and won't restart until it cools or sits for a minute
- • Stumbling, hesitation, or a flat spot when you put your foot down
- • Rough lumpy idle that comes and goes
- • Random misfires under load, particularly noticeable pulling up a motorway slip road
- • Sometimes nothing obvious at all except the light, if the signal only drops out occasionally
Possible causes
Causes commonly associated with P0320, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Failing crankshaft position sensor. This is the usual culprit. They get heat-soaked over the years and start dropping their signal when hot, which is why so many cars stall when warm and then restart cold
- 2. Camshaft position sensor playing up, less common than the crank sensor but worth ruling out, especially on engines that use the cam signal for sync
- 3. Damaged or corroded wiring and connectors in the sensor circuit. Engine bay heat and vibration crack the insulation and back out the pins over time
- 4. Water or oil contamination getting into the connector or harness, which is common on older diesels where the sensor sits low and exposed
- 5. A chewed up or oil-fouled reluctor ring (the toothed wheel the sensor reads), or excess play letting the gap wander
- 6. Open or short on the sensor's power feed or earth, so it never gets a clean reference to work against
- 7. Weak battery or charging fault giving low voltage, which can scramble the signal enough to set the code
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. Scan it and read off everything stored, not just P0320. If you see P0335, P0340 or misfire codes alongside it, that narrows down whether it's the crank side, cam side, or the harness common to both
- 2. Check the battery and charging system. Low or noisy voltage will give you erratic sensor readings, and there's no point chasing the sensor until the supply is solid
- 3. Get under the bonnet and physically inspect the sensor connectors and harness. Unplug them, look for green crusty pins, oil, water, or chafed wires near hot or moving parts. A lot of these turn out to be a duff connector rather than a duff sensor
- 4. Back-probe the sensor's reference voltage (around 5V on most setups) and earth with a multimeter, then watch the signal on a scope while cranking if you have one. A clean waveform that stutters when hot points straight at the sensor
- 5. Pull the sensor and check the reluctor ring for missing or damaged teeth, debris, and play. A clean signal needs a clean wheel running true
- 6. If the wiring, supply and reluctor all check out but the signal is still flaky, the sensor itself is your answer. ECM reprogramming or replacement is a last resort and rarely the issue
Common questions about P0320
If I clear the code, will it actually stay gone? +
Depends entirely on what set it. If it was a one-off low-voltage glitch from a flat battery, it might clear and never come back. But if you've got a heat-failing crank sensor or a corroded connector, clearing it just resets the clock. The light comes straight back the next time the engine gets hot or the wiring shorts out. Clearing it is a useful test, not a fix. If it returns within a few drives you've still got the underlying fault.
What am I risking if I just keep driving with it? +
The main risk is the engine cutting out on you without warning. Lose the crank signal at speed and the engine dies, you lose power steering and braking assistance, and you're coasting until you can pull over. That's a genuine safety problem on a motorway or at a junction. It won't usually destroy the engine, but an intermittent signal can also cause misfires that, left long enough, can hammer the catalytic converter. Don't sit on it.
How quickly do I need to sort this? +
Treat it as soon-ish rather than next-week-maybe. If the car is already stalling or struggling to restart, get it looked at before you next rely on it for anything important, because a sensor that's dropping out intermittently usually gets worse, not better. If you're only seeing the light with no driving symptoms yet, you've got a bit more breathing room, but I'd still book it in rather than ignore it.
Is it the sensor itself or just the wiring? +
Roughly speaking it's most often the crank sensor, but a fair chunk of these are connector and wiring faults, so don't just throw a sensor at it. Sensors are cheap enough that people fit one, the code comes back, and they're back to square one because the real fault was a corroded pin or a chafed earth. Always inspect and test the harness and connectors first. A new sensor on bad wiring fixes nothing.
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 →