P0335 — Crankshaft Position Sensor “A” Circuit Malfunction

Category

Powertrain → Sensors (Engine Timing & Position)

What it means (plain English)

The crankshaft position (CKP) sensor monitors crankshaft speed and position, sending signals to the ECM to control fuel injection and ignition timing.

A P0335 code means the ECM is not receiving a valid signal from the CKP sensor. Without this data, the engine may fail to start, misfire, or shut down unexpectedly.

Symptoms

  • Check Engine Light (MIL) illuminated
  • No-start or extended cranking
  • Engine stalling, especially when warm
  • Misfires or rough idle
  • Poor acceleration or limp/derate mode
  • Tachometer may not move during cranking

Priority Level

Very High —
Without crankshaft signal, the ECM cannot time injection correctly. This often results in a no-start condition or sudden engine shutdown while driving.

Common Causes

  • Failed CKP sensor (most common)
  • Damaged reluctor ring on crankshaft (missing or damaged teeth)
  • Wiring harness open/short (especially near sensor connector)
  • Corroded or loose CKP connector
  • Excessive metal debris stuck to magnetic sensor tip
  • ECM/PCM failure (rare)

How Pros Diagnose It (step-by-step)

  1. Scan tool — confirm P0335, check for companion camshaft sensor codes.
  2. Visual inspection — sensor wiring, connector, and mounting position.
  3. Check signal with oscilloscope — look for clean waveform during cranking.
  4. Resistance test sensor (compare to OEM spec).
  5. Inspect reluctor ring (flywheel or crankshaft) for missing/damaged teeth.
  6. Check for metal debris on sensor tip.
  7. Wiggle test harness during cranking to check for intermittent opens.

Likely Fixes

  • Replace failed CKP sensor
  • Clean sensor tip (if debris is present)
  • Repair or replace damaged wiring/connectors
  • Replace damaged reluctor ring/flywheel
  • Replace ECM only if all else checks out

Related/Companion Codes

  • P0336 — CKP Range/Performance
  • P0340 — Camshaft Position Sensor Circuit
  • P0016 — Crank/Cam Correlation Fault
  • P0727 — Engine Speed Input Circuit No Signal

Tech Notes (Quick Hits)

  • Duramax LB7/LMM/LML — heat soak failures are common; CKP sensor may work when cold, fail when hot.
  • Cummins ISX/ISB — harness rub-through at the block often causes intermittent P0335.
  • Powerstroke 7.3L/6.0L — CKP sensors are prone to magnetic debris buildup.
  • Always check for crank/cam correlation codes (P0016) — they often appear together.

Severity: Very High — Repair Immediately
A P0335 code means the ECM is not receiving a signal from the crankshaft position sensor. Without this data, your truck may stall, misfire, or fail to start at all. Replacing the sensor or repairing wiring is usually required to get back on the road.

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