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DTC codes / Chrysler codes / P1398

P1398 · ChryslerPCM Is Unable To Learn The Crankshaft Position Sensor's Signal

This code means the powertrain control module (PCM) cannot synchronize the crankshaft position sensor signal with the camshaft position sensor signal during the engine's learn routine. The PCM has detected that the crankshaft signal is present but erratic, intermittent, or out of expected timing, so it cannot establish a reliable reference for fuel injection and ignition timing.

SystemPowertrain
Code typeChrysler specific
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Intermittent engine stalling or a sudden loss of power while driving
  • Extended cranking before the engine starts, or a no-start condition
  • Rough running, misfiring, or poor fuel economy
  • A tachometer that reads erratically or drops to zero momentarily

Common causes, most likely first

  1. Failed or failing crankshaft position sensor
  2. Wiring damage (chafed, corroded, or broken wires) between the crankshaft sensor and the PCM
  3. Loose or damaged crankshaft sensor connector
  4. Debris or metallic particles on the crankshaft sensor tip or reluctor wheel
  5. Worn or damaged crankshaft reluctor wheel (missing teeth or incorrect gap)
  6. PCM software issue or internal fault preventing the learn procedure from completing
  7. Aftermarket or incorrect crankshaft sensor installed

How to diagnose and fix it

  1. Inspect the crankshaft position sensor and its connector for physical damage, corrosion, or loose pins
  2. Clean any metallic debris from the sensor tip and the reluctor wheel
  3. Check the sensor air gap and reluctor wheel condition according to Chrysler specifications
  4. Perform a wiggle test on the sensor wiring harness while monitoring live data to reveal intermittent faults
  5. Measure the sensor's resistance and compare it to the manufacturer's specification
  6. Use a scan tool to command a crankshaft learn procedure and verify that it completes successfully
  7. If the learn still fails, substitute a known-good OEM crankshaft sensor and retest before condemning the PCM

Why the crank learn keeps failing

  • A weak or failing camshaft position sensor can prevent the crankshaft learn from completing even when the crankshaft sensor itself tests good, because the PCM needs both signals to synchronize.
  • Metallic debris from a worn reluctor wheel or a failing sensor can accumulate on the sensor tip and cause an intermittent signal that only appears under certain RPM or temperature conditions.
  • Aftermarket crankshaft sensors often have a different magnetic strength or output waveform that the Chrysler PCM will not accept during the learn routine, so an OEM sensor is frequently the only reliable fix.
  • A poor engine ground or voltage drop on the sensor's ground circuit can corrupt the crankshaft signal without setting a separate ground fault code, so always verify ground integrity before replacing parts.
  • The code can be stored by a failed learn attempt after battery replacement or PCM reprogramming, and simply clearing it and re-running the learn procedure may resolve it if no hardware fault exists.

Can I keep driving with P1398?

You can usually drive the vehicle to a repair shop if the engine runs smoothly and the check engine light is steady, but avoid heavy acceleration, towing, or long trips because a sudden stall or no-start could leave you stranded. If the engine stalls, misfires, or the light flashes, stop driving and have the vehicle towed.

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 Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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