Following a cylinder head and timing belt repair, the check engine light was on with fault codes consistent with an overboost condition.

The vehicle had originally been brought in with mechanical engine damage caused by an incorrectly fitted timing belt, resulting in bent valves and damaged rocker arms. The cylinder head, valves, lifters and timing belt were repaired and the engine ran correctly afterwards. However, after the repair the check engine light was illuminated with fault codes related to overboost, and the codes returned after each road test once cleared. Prior to the original failure the vehicle had no faults logged.