Engine

P0339 — Crankshaft Position Sensor "A" Circuit Intermittent

Severity: high Drive with care, to a shop

What P0339 means

The engine computer reads the crankshaft position sensor to know engine speed and crank angle, which it needs to time spark and fuel. P0339 sets when that signal drops out or becomes erratic and then comes back. Usual causes are a poor connection, damaged wiring, or a worn sensor.

Symptoms

  • Check Engine light that comes and goes or stays on
  • Engine stalls suddenly while driving or idling
  • Hard starting or no-start, especially when warm
  • Rough idle, misfires, or hesitation
  • Loss of power and worse fuel economy
  • Engine cranks but takes a while to catch

Possible causes

  1. Worn or heat-damaged crankshaft position sensor
  2. Chafed, damaged, or corroded wiring harness
  3. Loose or corroded sensor connector, or a weak ground
  4. Metal debris or dirt on the sensor tip
  5. Damaged reluctor ring or excessive air gap
  6. PCM input circuit fault (rare)

How to diagnose

  1. Scan for codes and freeze frame data, and note any related codes such as P0335 or P0340.
  2. Inspect the sensor, connector, and wiring for rubbing, melting, oil, or corrosion, and check the connector lock.
  3. Wiggle the harness and connector with the engine running while watching RPM on a scan tool for dropouts.
  4. Remove the sensor and check the tip for metal debris or damage, and check mounting and fit.
  5. Test power, ground, and signal wire continuity with a multimeter per the factory wiring diagram.
  6. Measure the sensor resistance (inductive type) or view the waveform on a scope for missing teeth or dropouts.
  7. Inspect the reluctor ring for cracks or damaged teeth and verify the air gap.
  8. If all is good, check PCM power and grounds, and look for software updates.

Common fixes

  • Replace the crankshaft position sensor
  • Repair or replace damaged wiring and connectors, and clean the terminals
  • Restore the ground and secure the sensor mounting
  • Repair or replace the reluctor ring and set the correct air gap
  • Reprogram or replace the PCM (last resort)

Questions and answers

What does P0339 mean?

The PCM detected an intermittent loss or distortion of the crankshaft position sensor signal. Because it comes and goes, it is often mistaken for a random glitch.

Is it safe to drive with P0339?

It is risky, since the engine may stall without warning and then fail to restart. If you must drive, keep it to a short trip to a shop.

Will clearing the code fix it?

No. Clearing it only turns off the light, and the code will return until the cause is fixed. Check the connector, wiring, and sensor first.

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.