What does it mean?
The control module works out where each piston is and which stroke it is on by comparing the crankshaft position sensor signal with the camshaft position sensor signal. The two signals have a fixed relationship set by the timing belt or chain, and the module uses it to decide when to inject fuel and when to fire the coil. P033F is stored when that relationship is lost or drifts outside the allowed window: the correlation between the two signals no longer makes sense, or the module cannot match a camshaft pulse to the expected crankshaft angle at all. This is a serious fault because it usually means the mechanical timing has moved or that one of the signal sources has become unreliable, and continuing to run the engine in this state risks valve to piston contact on interference designs.
Symptoms
- Long cranking, hard starting or a complete no-start
- The engine cuts out while driving and may or may not restart
- Rough running, severe misfire and heavy vibration
- Rattling or chain noise from the front of the engine, especially in the first seconds after start-up
- Warning lamp on with reduced power and limp mode
- Erratic tachometer needle or an engine speed reading that jumps
Likely causes
- Stretched timing chain, worn guides or a failed hydraulic tensioner allowing the chain to jump a tooth
- Timing belt that has slipped, lost teeth or was fitted one tooth out at the last service
- Cracked, loose or slipped crankshaft reluctor ring, or a damaged camshaft trigger wheel
- Failing crankshaft or camshaft position sensor with an intermittent or noisy output
- Variable valve timing phaser stuck out of position or unlocked from its home position, often from low oil pressure
- Sensor wiring problems: chafed harness, damaged shielding picking up interference, corroded connector
- Loose crankshaft pulley or harmonic balancer with a sheared key
How to fix it
- Stop running the engine if a timing failure is suspected, since valve to piston contact can occur
- Read the correlation values in live data and compare the crankshaft and camshaft signals with an oscilloscope while cranking
- Remove the timing cover as required and check the marks, then measure chain slack, tensioner extension and guide wear
- Inspect the reluctor ring and camshaft trigger wheel for cracks, debris, damaged teeth and any movement on their mountings
- Check engine oil level, condition and pressure, because the chain tensioner and the variable valve timing phasers depend on it
- Test the position sensors for air gap, resistance where applicable, signal quality and connector condition
- Renew the timing components as a set where the manufacturer specifies it, set the timing correctly, then clear the code and verify the correlation values in live data