For 1990-2009 cars

Cause | Correction
--- | ---
Restricted oil supply hose | Inspect for restricted turbocharger oil supply hose.
Spun camshaft bearing |

1. Remove the oil supply hose. Refer to Turbocharger Oil Feed Pipe Replacement.
2. Visually inspect for correct alignment of the camshaft bearing oil hole.
3. Rotate the engine 1/2 turn and inspect the camshaft bearing oil hole for movement, indicating a spun camshaft bearing.