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Mileage stored in the ECM?


tomsbuick

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:)  I have enjoyed my 1990 coupe but I may put it in storage and disconnect the battery for a month or two.

My question is if there is no charge from the battery for a month will i loose the mileage count that is displayed

and will it go back to zero? Where is the mileage recorded and how can it be retained with no electric charge 

with a disconnected battery? Does the ECM just go to factory default with no battery current? Any comments appreciated.

189575269_Reattagoodpic.jpg.6cfb5d1070c418432ceac57edccfc1a9.jpg

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You will not lose your mileage. I think it is stored in the chip located in the BCM. Just charge up the battery and remove the lead to the Negative side of the battery and when you reconnect you will have everytning as it was when disconnected.

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When I put mine away I just connect a trickle charger.

If you disconnect the battery then hook it up later you will get a couple codes. At least I always do! The codes are for the radio losing the pre-set stations. I then reset my stations and clear the codes then it's all set and good to go.

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The mileage is stored in the IPC I changed both the ECM and BCM and there was no effect on the mileage. When I purchased those units I was asked for the mileage and I gave a number I thought it was (95,000) because the IPC was blank. I installed the ECM because it was dropping out #6 injector. I changed the BCM hoping that would fix the IPC (It didn't) when I fixed the IPC the mileage came up to 205,000 Heres a hint for ya, if your going to store the car and want to keep the pre-learned features Take a cord from an old phone and cut off the end that goes to the phone (make sure you know what wire is + and - ) connect the wires to a 9V battery and plug the other end into the cigarette lighter socket now you can remove the battery from the car for storage. Every now and then check the 9V with a volt meter if it shows signs of discharge re-hook the car battery and change the 9V then disconnect the car battery.

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The mileage is stored in the IPC I changed both the ECM and BCM and there was no effect on the mileage. When I purchased those units I was asked for the mileage and I gave a number I thought it was (95,000) because the IPC was blank. I installed the ECM because it was dropping out #6 injector. I changed the BCM hoping that would fix the IPC (It didn't) when I fixed the IPC the mileage came up to 205,000 Heres a hint for ya, if your going to store the car and want to keep the pre-learned features Take a cord from an old phone and cut off the end that goes to the phone (make sure you know what wire is + and - ) connect the wires to a 9V battery and plug the other end into the cigarette lighter socket now you can remove the battery from the car for storage. Every now and then check the 9V with a volt meter if it shows signs of discharge re-hook the car battery and change the 9V then disconnect the car battery.

 

I don't want to seem argumentative but I believe the odometer reading and VIN is stored in the EEPROM (chip) inside the BCM. The EEPROM can be moved from one BCM to another when you are replacing the BCM to keep the mileage and VIN reading correct for your car.

 

Take a look at the photos below. Note that the first photo says the EEPROM cannot be moved from one VEHICLE to another. That is because you would be moving the stored mileage and VIN to another car which would be against Federal law.

 

The VIN can be read on the CRT when you are in the onboard diagnostics. I'm not sure about the mileage reading.

1530072822_Screenshot-2017-12-2189Reatta-47-8D2-BCMTroubleCodeDiagnosispdf.png.71b3feb08cdd5155463cb17877e462c7.png

565889395_Screenshot-2017-12-2189Reatta-47-8D2-BCMTroubleCodeDiagnosispdf(1).png.594b94751676d85945a585bc8d1377e5.png

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Correct - what he ^ said!!

 

Come to think of it I believe your right! I completely forgot about having to install the old  prom into the unit. My bad.

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Come to think of it I believe your right! I completely forgot about having to install the old  prom into the unit. My bad.

 

Sir,

 

It was not my intent to "correct" you but rather to confirm something that I have learned the hard way.  :rolleyes:  Isn't it funny how we learn more from our failures than our successes!!

 

I really appreciate your contributions to this forum!!  Please continue to share your thoughts as I have learned lots from reading your input and suspect others agree.

 

Thank you for sharing your incredible knowledge of GM's engineering and repairs!!

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Sir,

 

It was not my intent to "correct" you but rather to confirm something that I have learned the hard way.  :rolleyes:  Isn't it funny how we learn more from our failures than our successes!!

 

I really appreciate your contributions to this forum!!  Please continue to share your thoughts as I have learned lots from reading your input and suspect others agree.

 

Thank you for sharing your incredible knowledge of GM's engineering and repairs!!

 

What a nice way to make my day, thank you and may all have a very Merry and safe Christmas and New Year.

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