Code P066, Cruise Control Engine Rpm Too High: Notes
WARNING: This page is about a different car, the 1995 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Code P066 will set when engine speed is greater than 4800 RPM with cruise engaged. This may occur on slippery pavement, extended wide open throttle acceleration, or for some other mechanical problems (such as transaxle slippage). Under these conditions, Code P066 will set and should be considered normal. Vehicle operator should be advised why cruise control disengaged. Clear code and road test vehicle to verify normal operation.