That will definitely reset the readiness monitors, not sure about the rest though.
Any benefit to resetting PCM?
- Thread starter Joseph
- Start date
That will definitely reset the readiness monitors, not sure about the rest though.
I just tried this after installing a throttle body spacer on my YJ 2.5L Battery seems to be dead now. Won't turn over and headlights won't turn on. Any Ideas?
I’ve recently done this dance. The headlight part of the instructions have nothing to do with draining the system bc the battery is connected when you do that part. I don’t know what it accomplishes that turning the key on and off won’t do, but I didn’t fight it.
Clearing codes, selecting relearn with my device, and removing the battery terminals with the lights on and key on did not reset my PCM and update the cam/crank learning like I hoped it would. Nor did only touching the cables together for well over 30 seconds.
However, the Cam/Crank relearn did properly happen after I followed these instructions. I still think the headlight part was odd since the battery is connected at that point of the instructions.
All I know is that following these instructions worked after other methods didn’t work.
Last edited:
You missed the "Turning the headlights on when the battery is disconnected just places an additional electrical draw/load across the PCM since it ultimately shares a power connection with the lights. Doing that simply helps to reset the PCM more quickly."
I didn’t miss anything. That otherwise useful knowledge doesn’t apply to these instructions. I understand that classic move and I tried multiple times to drain the system (key on, accessories on, lights on) without success…before I found these instructions.
Cycling the lights is done with the battery connected if you follow the directions (which are posted elsewhere as well).
These instructions say to connect your battery and then cycle your lights after you have turned the ignition to run. I did this dance two days ago so I’m privy to what didn’t work and what ultimately worked,
Cycling the ignition after reconnecting the battery makes more sense to me since I do so multiple times when installing the Banks turbo tune. But cycling the lights with the battery connected seems a bit odd…I did it anyways and the relearn was finally achieved by following the directions.
Next time I’ll skip cycling the lights and only cycle the ignition to see if still updates.
Last edited:
You would think there would be diodes in the PCM to stop it back-powering things like the lights, LOL. Andy
With that response we'll have to agree to disagree that you understood what I said.
There is nothing to agree or disagree on.
Post #7 was a question about cycling the lights with battery connected (per the instructions in post #2).
In post #8, you explained what cycling the lights do when the battery is NOT connected. That didn’t answer the question.
@jjvw I’m also skeptical about the lights being cycled with the battery connected and ignition in run (w/ engine off). I’m stoked the directions worked, but I also thought the cycling lights part seemed odd.
I’ll do the manual relearn without cycling the lights next time I mess with the OPDA.