Check engine light diagnostics

A code is not a diagnosis. The parts store that reads “P0171” for free and sells you an oxygen sensor is guessing; the code means the engine is running lean, and the sensor is only one of a dozen possible causes.

Our diagnostic fee buys an hour of a technician’s time with professional scan tools, factory wiring diagrams and a scope. We read the codes, look at the live data the engine computer was seeing when the fault was set, test the suspect components and write down what we found and what it will cost to fix. If you have us do the repair the fee is credited toward it.

A flashing check engine light means stop driving. It indicates a misfire severe enough to damage the catalytic converter. Pull over, call us and we will arrange a tow.

A steady light is not an emergency but should not be ignored either, partly because a second fault can hide behind the first. Most of the time the cause is something modest: a purge valve, a coil, a vacuum leak, a worn plug. Occasionally it is a loose gas cap, in which case we clear the light and send you home without charge.