What Is P0016?
P0016 is a correlation code. The ECU uses camshaft and crankshaft position signals to synchronise fuel injection and spark timing precisely. The crank signal tells the ECU when the piston reaches top dead centre, and the cam signal tells when a specific intake valve opens. These signals must match exactly — if the cam is rotating at the wrong phase relative to the crank, they fall out of correlation and P0016 is triggered.
This code is serious because it usually indicates a stretched or slipped timing chain, faulty sensors, or damaged sprocket teeth. An engine with P0016 will either not start or run very rough if it does.
Common Symptoms
- Engine will not start or cranks but won't run
- Severe rough idle or stumbling if it manages to run
- Check engine light flashing or solid
- Rattling or knocking from timing area when cranking
- Severe hesitation and lack of power if somehow running
Common Causes
How to Diagnose P0016
Check Sensor Connectors
Inspect the crankshaft and camshaft position sensor connectors for corrosion, loose pins, or damaged wiring. Clean any corroded connectors and reseat them fully. Sometimes a loose sensor connector can trigger P0016 without actual timing being wrong. Clear the code and retest.
Test Crank and Cam Sensor Signals
Connect an OBD scanner and monitor the camshaft and crankshaft position sensor signals in live data mode. Both should show regular square-wave signals that oscillate smoothly. If either signal is frozen, erratic, or missing, that sensor is faulty and needs replacement.
Inspect Timing Cover for Chain Rattle
Ask a helper to crank the engine while you listen near the timing cover (front, below cylinder head). A severely stretched or slack chain will rattle loudly. A healthy chain is nearly silent. Loud metallic rattling indicates the chain needs inspection or replacement.
Check Timing Marks Visually
If the vehicle has access windows or if you can safely remove the timing cover, inspect the timing marks on the crankshaft and camshaft sprockets. They should align with witness marks on the engine block. Misalignment indicates the chain has skipped teeth or stretched. This requires removing covers — a professional job on most cars.
Check Oil Level and Condition
Low or dirty oil starves the timing chain of lubrication and accelerates wear. Check the dipstick and condition. If oil is black or smells burnt, perform an oil change. Sludge buildup can cause sensor signal interference, contributing to P0016.
Verdict
P0016 is a serious code. Start by checking sensor connectors and oil condition — cheap fixes that might work. If sensors test okay, the timing chain is likely stretched or slipped, requiring professional timing system inspection and possible replacement. This is a £1000–£2500 repair in most cases. Do not drive the car.
