P0321

What it means

P0321 is the generic code for a range or performance fault in the ignition or distributor engine speed input circuit. The engine control unit has seen an engine speed signal from the ignition system or distributor that does not look plausible, for example an erratic or noisy signal, or one that disagrees with other sensors such as the crankshaft or camshaft position sensor. The exact signal source depends on the engine, as some use a distributor pickup and others use a coil-driven or crank-derived speed signal.

Symptoms

• Engine misfires or runs roughly
• Hesitation or poor acceleration
• Intermittent stalling or cutting out
• Hard starting or long cranking
• Rev counter flickering, dropping to zero or reading wrongly
• Engine warning light on, possibly with limp mode

Possible causes

• Damaged, corroded or loose wiring or connector in the engine speed signal circuitlikely
• Faulty or failing crankshaft or distributor pickup sensor giving an erratic signallikely
• Incorrect sensor air gap, or metal debris or contamination on the sensor or reluctorpossible
• Worn distributor, shaft play or damaged reluctor or trigger wheel (where fitted)possible
• Electrical interference from faulty ignition leads, coils or poor earthspossible
• Timing chain or belt wear or jumped timing causing the signals to disagreerare
• Faulty engine control unitrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine speed, load and temperature when the fault set, and check for related crank, cam or misfire codes.
2. Check the rev counter and engine speed reading on live data during cranking and at idle, looking for dropouts or spikes.
3. Inspect the wiring and connectors to the speed sensor or distributor for chafing, heat damage, water ingress, corrosion and loose pins, and wiggle test with the engine running.
4. Inspect the ignition leads, coils and earth connections for damage or poor contact that could cause electrical interference.
5. Check the sensor mounting, air gap where adjustable, and the sensor tip and reluctor or trigger wheel for debris, damage or wear.
6. Check the sensor resistance or output against the manufacturer specification, which varies by model and engine.
7. Use an oscilloscope to compare the crank and cam signal patterns for dropouts, noise or timing disagreement.
8. Check the mechanical timing and, where fitted, distributor shaft play if the signals disagree and the electrical checks pass.

How to fix

• Repair or replace damaged wiring, and clean or replace corroded connectors in the speed signal circuit.
• Replace the faulty speed or position sensor or distributor pickup, and set the air gap where specified.
• Clean off debris or replace a damaged reluctor or trigger wheel, or overhaul or replace a worn distributor.
• Replace faulty ignition leads or coils and restore good earth connections to remove interference.
• Correct the mechanical timing or replace worn timing components if they are the cause.
• Only after all other causes are excluded, diagnose and replace the engine control unit, following the manufacturer procedure.

Can I keep driving?

Nearby codes

• P0320GenericIgnition/Distributor Engine Speed Input Circuit
• P0322GenericIgnition/Distributor Engine Speed Input Circuit No Signal