Ignition

P0321 — Engine Speed Input Signal Out of Range

Severity: medium Drive with care, to a shop

What P0321 means

The PCM continuously compares the engine speed signal from the crankshaft position sensor (or the distributor pickup on older engines) with what it expects and with other sensor signals. That signal is used to calculate ignition timing and fuel injection. P0321 is set when the signal is erratic, drops out or does not make sense for how the engine is running.

Symptoms

  • Check Engine Light on
  • Tachometer jumping or dropping to zero
  • Rough idle
  • Misfires and hesitation under acceleration
  • Hard starting or no-start
  • Intermittent stalling while driving

Possible causes

  1. Failing crankshaft position (engine speed) sensor
  2. Damaged wiring or corroded, loose connector at the sensor
  3. Faulty distributor or its internal pickup (older engines)
  4. Wrong sensor air gap or metal debris on the sensor tip
  5. Failing ignition module
  6. Slipped timing belt or chain
  7. PCM input circuit fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data; look for related camshaft sensor or misfire codes
  2. Inspect the crankshaft sensor connector and harness for corrosion, chafing, oil and a poor latch
  3. Watch RPM on a scan tool while cranking: the signal should appear right away and stay steady
  4. Remove the sensor, check its tip for debris or damage, and verify the mounting and air gap
  5. Test the sensor per specs: resistance for an inductive type, or supply and signal for a Hall type
  6. Check the wiring to the PCM for opens, shorts to ground or voltage, and wiggle the harness with the engine running
  7. Compare crankshaft and camshaft signals on a scope and inspect the reluctor wheel for damaged teeth
  8. Verify timing marks and the condition of the belt or chain

Common fixes

  • Replace the crankshaft position sensor
  • Repair the wiring or replace the connector, and clean the contacts
  • Replace the distributor, its pickup or the ignition module
  • Correct the valve timing and replace the belt or chain
  • Repair or replace the PCM only after the fault is confirmed (rare)

Questions and answers

What does P0321 mean?

The PCM judges the engine speed signal from the crankshaft or distributor sensor to be unreliable. The sensor itself or its wiring is the most common cause.

Can I drive with P0321?

Only a short distance, such as to a shop. The engine can stall at any time and may not restart, so don't put off diagnosis.

Will replacing the crankshaft sensor fix P0321?

Not always. Check the connector, wiring, air gap and reluctor wheel first, or the code may come back after the new sensor goes in.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.