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Q: Can you have a bad PCM but have no check engine light on?

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My vehicle has all the necessary essentials to run ( spark, air, fuel. ) Witch makes me think it could be the pcm. But I do not have a check engine light on. Is it possible to have a bad PCM but not have a check engine light on?

A: Hello and thank you for contacting YourMech...

Hello and thank you for contacting YourMechanic. PCM's typically fail for one of two reasons: voltage overloads (often due to a short in a solenoid or actuator circuit) or environmental factors (corrosion, thermal stress or vibration). If water gets inside a PCM, it can short circuits and set up irreversible corrosion that ruins electronic connections. The PCM should give you a code for P0600 through P0606 indicating that the computer has a processor error.

However, if the PCM is corrupt, then just like a desktop computer, there is no accessing anything and no codes are put out for the computer would have no way of sending a signal. If you need further assistance troubleshooting your PCM, then seek out a technician, such as one from YourMechanic, to come to your location for an inspection.

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