P0335: Crankshaft Position Sensor circuit. Sometimes won't start. Sometimes drives fine.

P0335: Crankshaft Position Sensor circuit. Sometimes won't start. Sometimes drives fine.

Amigo, this code is one of those weird ones. Some cars throw P0335 and the engine runs fine. Others throw it and won't even crank-start. Same code, totally different driveability. Let me explain why.

The crankshaft position sensor (CKP) tells the PCM exactly where the crankshaft is at every moment. The PCM uses that information to fire the spark plugs at the right time and pulse the injectors at the right time. No CKP signal at all = engine cannot start. Intermittent CKP signal = engine starts but stumbles, dies, or runs rough.

P0335 specifically means the PCM can't find a valid CKP signal during cranking, OR the signal looks corrupted. The sensor itself, the wiring, the PCM input, or the reluctor wheel on the crankshaft can all cause this code.

Symptoms by severity

• Mild: Check engine light, occasional rough idle, no real driveability problem. Code stored after a brief signal glitch.
• Moderate: Engine stalls randomly, then restarts after a minute. Often happens when hot. The sensor is failing intermittently, especially as it heats up.
• Severe: Engine cranks but won't start. No spark, no fuel pulse. PCM never gets a signal so it doesn't know when to fire.

Diagnostic, in order

Step 1: Check for related codes. P0336 (range/performance) often paired with P0335. P0340 (CMP) sometimes appears alongside on engines that share the same wiring harness section. If you have multiple sensor codes, suspect a shared wiring problem (rodent damage, chafe point) before condemning sensors.

Step 2: Visual inspection. The CKP sensor on most engines is on the bell housing area, lower side of the engine, often just above the starter or at the rear of the engine. Pull the connector. Look for corrosion, broken wires, oil saturation. Common failure mode: oil leak from the rear main seal saturates the connector and corrodes the pins.

Step 3: Resistance test. Most CKP sensors are 2-wire or 3-wire Hall effect or magnetic. Check the spec for your engine — usually 200-2000 ohms across the sensor terminals. Open circuit or shorted = sensor bad.

Step 4: Check the reluctor wheel. The CKP reads pulses from a toothed wheel on the crankshaft. If the wheel teeth are damaged, missing, or covered in metal debris from a previous engine event, you get bad signal. Pull the sensor and visually inspect the wheel through the hole. If it looks chewed up, you're looking at internal engine work.

Step 5: Check wiring continuity from sensor to PCM. Backprobe the PCM connector for the CKP signal wire. With ignition on, you should see voltage there matching the sensor type spec. If voltage doesn't reach the PCM, you've got a broken wire somewhere in the harness.

Step 6: Replace the sensor. If everything else checks out, swap the sensor. About $30-$120 for the part, 15-60 minutes of labor depending on access. Most failures end here.

Heat-cycle failure pattern

This morning I had a Chevy Malibu with P0335 — owner said it stalls 20 minutes into a drive then restarts after sitting for 15. Classic heat failure on a CKP. Cold sensor reads fine. Hot sensor opens up internally. Replaced it for $45 in parts, problem solved. Heat-cycle failures are why some sensors test "good" when the car is cool and you can't reproduce the issue at the shop.

If you suspect heat-cycle failure, take a hair dryer to the sensor while the engine is running. If you can make it stall by heating the sensor, you've confirmed it.

Parts

• CKP sensor — $30-$120 (OEM is worth the extra $20 here)
• Connector pigtail kit — $15-$25 if connector is damaged
• Rear main seal (if oil leak is the root cause) — $40 in parts, $400+ in labor (transmission has to come out)

What people get wrong

Don't replace the PCM. Almost never the PCM. People throw $400 PCMs at this and the actual problem was a $30 sensor.

Don't ignore it because the car drives fine. Even if it's running OK now, an intermittent CKP signal will eventually leave you stranded somewhere.

Related codes: P0016 (CKP/CMP correlation) can be triggered by the same root cause. P0300 (random misfire) sometimes appears with P0335 because the PCM can't time fueling correctly with bad crank data.

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