P0335 Crankshaft Position Sensor A Circuit Malfunction
The sensor that tells the computer where the crankshaft is has dropped out — without it the engine may stall or refuse to start at all.
Misfire & ignition
The crankshaft position sensor is the engine's primary timing reference: it tells the ECU exactly where the crank is so spark and injection land at the right moment. P0335 means that signal is missing, erratic, or out of spec. This is one of the few codes that can leave you on the roadside, because an engine with no crank signal generally will not run.
Diagnose P0335 on your specific vehicle Add your year, make and model for ranked causes, repair videos and the exact parts you needCan I keep driving?
Driveable
Risky. Even if it is running now, the failure mode is a sudden stall — potentially in traffic, with power steering and brake assist dropping away. Treat it as urgent.
How serious
High. This is a stranding code. Failures are frequently heat-related, which produces the classic pattern of stalling once warm and restarting after it cools.
Symptoms you'll notice
- Engine cranks but will not start
- Stalls without warning, often once fully warmed up, then restarts after cooling
- Intermittent hard starting
- Tachometer dropping to zero or jumping erratically while driving
- Misfire or hesitation at speed
What causes P0335
Ordered by what to check first — how likely each cause is, weighed against what it costs to rule out. Working down the list in order is what stops you replacing an expensive part to fix a cheap problem.
Failed crankshaft position sensor
The most common cause. The sensor sits low on the block near the crank pulley or bellhousing, exposed to heat and road spray, and typically fails intermittently when hot before dying outright.
Damaged wiring or connector
Because of where it lives, the harness takes abuse from heat, oil and debris. Check the connector for oil intrusion — a leaking front main seal soaking the plug is a common and easily-missed root cause.
Damaged reluctor ring or tone wheel
The sensor reads teeth on a ring attached to the crank. A cracked ring or teeth damaged during previous work produces a signal that comes and goes with engine speed.
Incorrect air gap after replacement
Some designs need a specific clearance between sensor tip and reluctor. Too far and the signal is too weak to read; a sensor installed without its spacer will set this code straight away.
Metal debris on the sensor tip
These sensors are magnetic and collect swarf. On an engine that has had internal work or is wearing badly, a coating of metal filings blinds the sensor. Worth pulling and wiping before condemning it.
How to diagnose it
- Confirm whether the tachometer moves while cranking — a completely dead tach during cranking is a strong crank-sensor signature.
- Inspect the connector for oil contamination and the harness for heat damage.
- Back-probe the sensor while cranking with a multimeter or scope to see whether it produces a signal at all.
- Pull the sensor and check the tip for metal debris and physical damage, and inspect the reluctor teeth through the opening.
- If the fault is heat-related, try to reproduce it warm rather than chasing it on a cold engine, where it will often test fine.
Parts you might need
Tools for the job
- Multimeter
- OBD-II scanner with live data
- Oscilloscope (ideal but optional)
Related trouble codes
- P0340 — Camshaft Position Sensor A Circuit Malfunction (Bank 1)
- P0016 — Crankshaft Position — Camshaft Position Correlation (Bank 1, Sensor A)
- P0300 — Random/Multiple Cylinder Misfire Detected
Fitment matters. Causes and parts above are the common cases for P0335 across vehicles. The specific part numbers, procedures and torque specs vary by year, make, model and engine — always confirm against service data for your vehicle before buying parts or starting work.