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Posted

Question anyone? 07' Chev Silver 5.3 newer model. Question is if the ECM sees a code, will that code be stored in the ECM non volatile memory until it's either erased or fixed regardless of how long the battery has been disconnected for does it get erased by disconnecting the battery for an extended period.

Posted

could be either, theres a battery in the pcm so if that battery is still charged the code may not disappear. some vehicles hold codes for life even if they have been cleared. you can buy a cheap code reader for about $20 that will read and clear codes

Posted

Thanks Richard, long story short buddy said his truck was running really rough and check engine light illuminated but then he had disconnected the battery for at least 2-3+ weeks. When I hooked up a code reader no code there? I was wondering if he was mistaken about the check engine light or code got erased due to battery disconnection. Sounds like the latter, thanks for the info.

Posted

Yeah these computer will only hold that memory for a little while. Usually all it takes is having the battery unhooked for like an hour and it clears the most recent codes. If the fault is a permanent or hard fault it would trip the code straight away when the ignition was turned on again, otherwise it would take time for the fault to come back.

 

Kinda wish things were like heavy duty equipment/trucks. The PCM holds data for pretty much forever, they will give mileage, hours, fuel usage and all that jazz for the life of that engine/PCM it was connected to.

Posted

There are current and history codes current can be erased by disconnecting the battery for a couple of minutes but will come back if the issue isn't fixed, history codes will remain until after the problem is fixed and then can be cleared with a scanner.

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