What Are the Symptoms of a Bad Powertrain Control Module?
by Jen DavisUpdated August 01, 2023
Running Poorly
The PCM is what ultimately controls and regulates your fuel system. Different sensors in the engine send the PCM data about what the engine is doing. The PCM then adjusts the fuel mixture based on this data. If the PCM is not working properly, odds are that the fuel mixture will not be right. The vehicle may be receiving too much fuel or too little. If it is not getting enough fuel, it will cough, choke, sputter and may even stall. If it is getting too much fuel, your fuel economy will decrease and your exhaust emissions will increase.
Will Not Run
In some cases, a PCM problem will cause the vehicle not to run at all. The PCM's functions include positioning the crankshaft and controlling the ignition spark and timing. If there are problems with how the PCM performs these functions, the vehicle will not run and may even incur damage.
Dashboard Error Lights
If your PCM is malfunctioning, you can expect to see almost every error light imaginable appear and disappear at some point. The PCM controls and interprets sensor readings, so if it is not doing this properly, you can expect to see your "Check Engine" light, your "ABS system" light and a variety of others flash on and off.
Emissions
The PCM controls your vehicle's fuel and emissions system. If your PCM is not functioning properly, your car may fail its emissions test, emit too much smoke, emit colored exhaust (white, blue or black, depending on the issue) and may smell like fuel.
Writer Bio
Jen Davis has been writing since 2004. She has served as a newspaper reporter and her freelance articles have appeared in magazines such as "Horses Incorporated," "The Paisley Pony" and "Alabama Living." Davis earned her Bachelor of Arts in communication with a concentration in journalism from Berry College in Rome, Ga.
