PCM swap
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Only thing I would be concerned with is if you removed any other mods that would take the motor outside the ability of the factory tune. Otherwise, just do it. SHould not be a problem.
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No other mods......all stock
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How is a relearn performed?
Always disconnect the negative battery terminal on a pcm swap. Its not worth it for 2 minutes of work.
When ever you change the PCM, or T.B replacement you need to do a T.B relearn.
You also heed to do it if you replace the T.B.
Just ask any tuner or mechanic and they will tell you the same.
The OP did not change the Throttle body and did not modify his ride. He just loaded a Diablo tune on to an Unlocked PCM. That changed the factory tune to a Diablo tune. He still has the factory PCM with the factory tune. When he puts the PCM back in that came from the factory, the Throttle body could care less. It will operate on the parameters set by the Factory PCM. The Throttle body does not have memory!!
Now, if you would have replaced the TB and then when back to a factory setting you are talking about a modification that would require a re-learn. But he did not replace the TB.
I do it using HPTuners which is the best way to do it.
Or
1)Turn your ignition to the “ON” position. Do not start.
2) Wait for the warning lights to go out. The Check Engine Light may remain on but that’s OK.
3) Next Slowly depress the accelerator pedal all the way to the floor.
4) Slowly release the accelerator pedal until it’s all the way back up.
5) Now Turn the ignition to the “OFF” position.
6) After that just start up again and you done.
In some rare cases you may have to repeat this procedure if it only runs and will not come out of idle.
Whatever. You do it your way and I'll do it the proper way. This is mentioned in all Mopar service manuals to synchronize them with each other. But you must know better. lol
I would like to see the section in the service manual that talks about swapping a Diablo unlocked PCM and re-installing the stock factory PCM.
The PCM directs the TB based on a lot of factors. The TB in itself and the sensors associated with it will perform according to the PCM commands from his stock PCM as if it just came from the factory. The PCM does store the sensor values for a limited time. When the OP puts back in his factory PCM, the values for all the sensors that were present before he swapped PCM's will be used.
However, what is the harm in doing this😃
1)Turn your ignition to the “ON” position. Do not start.
2) Wait for the warning lights to go out. The Check Engine Light may remain on but that’s OK.
3) Next Slowly depress the accelerator pedal all the way to the floor.
4) Slowly release the accelerator pedal until it’s all the way back up.
5) Now Turn the ignition to the “OFF” position.
6) After that just start up again and you done.
Have a good day sir!
The PCM directs the TB based on a lot of factors. The TB in itself and the sensors associated with it will perform according to the PCM commands from his stock PCM as if it just came from the factory. The PCM does store the sensor values for a limited time. When the OP puts back in his factory PCM, the values for all the sensors that were present before he swapped PCM's will be used.
However, what is the harm in doing this😃
1)Turn your ignition to the “ON” position. Do not start.
2) Wait for the warning lights to go out. The Check Engine Light may remain on but that’s OK.
3) Next Slowly depress the accelerator pedal all the way to the floor.
4) Slowly release the accelerator pedal until it’s all the way back up.
5) Now Turn the ignition to the “OFF” position.
6) After that just start up again and you done.
Have a good day sir!
It will hold value for a short time in some cases, but I have had it not retain the values for the T.B. a few times after a few days.
Also, depending on how long you had the unlocked PCM in the car, the T.B. is most likely still being used with it, the resistance in the rheostat in the T.B. starts to change over time and because the original PCM is not learning those gradual changes, it ends up out of sync. when it's put back in at a later time. It often needs to be retaught to make up the difference for it to be 100% in sync.
I had some people say it made a big difference in how the engine acceleration improved after doing it, and for a few it did nothing. Still better to do it then not just to see if it does.
I look for any improvement I can find.
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