P0322 Ignition/Distributor Engine Speed Input Circuit No Signal

The definition

P0322: Ignition/Distributor Engine Speed Input Circuit No Signal.

P0322 is a powertrain code (the engine or gearbox), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.

What to check first

Cheapest and fastest checks first:

1. Check power and earth at the module first - a module with no supply cannot answer.
2. Check the two data-bus wires for continuity and for a short between them.
3. Scan the other modules: if several report the same module missing, the fault is at that module rather than on the bus.

What actually causes this on a VAG

This is the same engine speed input as P0321, but here the ECU saw nothing at all. Without that signal the ECU doesn't know where the crankshaft is, so it shuts off fuel and spark - which is exactly what it's designed to do. The usual picture is an engine that cranks over normally but won't fire, or one that cut out without warning while driving, with the rev counter sitting at zero while it turns over. On VAG cars this normally points at the crankshaft-mounted engine speed sensor (G28) and its wiring, though it's worth having the manufacturer-specific description read too. One important caveat before anyone spends money: a long spell of cranking on an engine that won't start for some entirely different reason can log this code by itself, so on a no-start it's a lead to check, not proof the sensor has failed.

Most likely causes, in order

1. Failed or loose engine speed sensor. These fail outright as well as intermittently, and a dead one gives exactly this - cranks, no start, no engine speed shown. A sensor that has worked loose or isn't seated to the correct depth can end up too far from the toothed wheel to read anything, which looks identical to the ECU, so check it's fully home and its bolt tight before ordering. It's usually an inexpensive part, though it can be awkwardly placed.
2. Broken wire or disconnected plug. A plug knocked off or a loom damaged during other work in that area will produce a total loss of signal just as convincingly as a failed sensor, and oil or coolant tracking down the harness from a leak above can do the same over time. Especially worth checking if the problem appeared straight after a service, clutch or gearbox job. A visual inspection and a continuity check at the ECU end will separate the two.
3. Damaged trigger wheel. Damage to the toothed wheel the sensor reads leaves it with nothing recognisable to count. Less common than the sensor or its wiring, and generally found once those have been ruled out - but if a sensor has been destroyed or displaced, the wheel is worth a look while everything is apart.

Worth knowing: Before anything is bought, have someone watch the engine speed reading on a scan tool while the engine is cranked. If it stays at zero, the fault really is in this circuit. If it reads normally, the code was probably logged by the long cranking rather than causing it, and the search should move on - fuel supply, immobiliser and ignition all produce a very similar cranks-but-won't-start. On a car that stopped suddenly and won't restart, a failed timing belt also needs ruling out early, because repeated cranking on a broken belt can make the damage worse.

Common questions

What does P0322 mean?

P0322 means Ignition/Distributor Engine Speed Input Circuit No Signal. This module has stopped talking on the car's data network, so nothing else can hear it.

Can I drive with P0322?

The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.

Related reading

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