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DTC codes / P03xx · Ignition system and misfire / P0339

P0339Crankshaft Position Sensor 'A' Circuit Intermittent

P0339 means the engine computer detected an intermittent signal from the crankshaft position sensor 'A' circuit, so the voltage or timing from that sensor dropped out or glitched rather than failing completely. The computer stores this code when the signal is present most of the time but momentarily disappears or becomes erratic during engine operation.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Check engine light illuminated, often with no other noticeable symptoms
  • Engine may stumble, misfire, or hesitate briefly under acceleration
  • Intermittent stalling or a no-start condition that comes and goes
  • Tachometer needle may jump or drop unexpectedly while driving
  • Rough idle or surging that appears only on some trips
  • Hard starting or extended cranking on occasion

Common causes, most likely first

  1. Faulty crankshaft position sensor with an internal intermittent connection
  2. Damaged or chafed wiring in the sensor harness, especially near hot or moving components
  3. Corroded, loose, or backed-out terminals at the sensor connector or engine computer
  4. Excessive air gap or debris on the sensor tip or reluctor wheel
  5. Worn or damaged reluctor wheel teeth or a loose harmonic balancer
  6. Electrical interference from a failing ignition component or poor ground
  7. Engine computer internal fault on the crank signal input circuit

How to diagnose and fix it

  1. Inspect the sensor connector and harness for corrosion, chafing, or loose pins, and repair as needed
  2. Check the sensor air gap and clean any metal debris from the sensor tip and reluctor wheel
  3. Measure the sensor resistance and compare it to the manufacturer's specification while wiggling the harness
  4. Back-probe the signal wire at the computer and monitor the crank signal on a lab scope while tapping and flexing the harness
  5. Check for a loose or damaged reluctor wheel or harmonic balancer that would cause an erratic signal
  6. Replace the crankshaft position sensor if the signal drops out during the wiggle test or scope pattern is erratic
  7. Clear the code and perform a road test with the scan tool recording to confirm the intermittent signal is gone

Why an intermittent crank signal fools everyone

  • A sensor that tests fine when cold and stationary can still fail intermittently once heat and vibration affect an internal break in the winding or connector.
  • Many P0339 cases are caused by a rubbed-through signal wire near the accessory belt or exhaust manifold rather than by the sensor itself.
  • A failing ignition coil or poor engine ground can induce electrical noise into the crank signal circuit and set this code without any sensor fault.
  • The code does not always mean the sensor is dead; a loose reluctor wheel or a failing harmonic balancer can produce the same intermittent dropout.
  • Technicians who replace the sensor without a wiggle test or scope capture often see the code return because the harness fault was never addressed.

Can I keep driving with P0339?

You can usually drive short distances to a repair shop, but avoid hard acceleration, towing, or long highway trips because an intermittent crank signal can cause sudden stalling or a no-start. If the engine stalls or cranks without starting, stop driving and arrange a tow.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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