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Why are you not supposed to PCM reset if tuned?

Posted: Thu Apr 18, 2019 9:54 pm
by OopsUpsideYerHead
I recently changed tire sizes on my 2017 F150. My truck is used, have no way to check with former owner if it has a tune. It does have a CAI & borla exhaust, so it is possible. If I change the tire size in Forscan it causes the wrench light to come on, to reset that I'm supposed to reset PCM but a warning pops up saying not to do it if tuned.

I'm curious why you shouldn't reset PCM if tuned? What would the consequences be? And if possible, is there a way to determine if my truck is tuned?

Re: Why are you not supposed to PCM reset if tuned?

Posted: Mon May 13, 2019 12:07 pm
by t4thfavor
I would assume (knowing other tuned vehicles) that it might screw up your ability to return to stock using the prior owners tuning tool/computer. It's pretty safe bet that the P/O returned your truck to stock and sold the tuner for extra cash prior to turning it in or selling. And that's IF there was a tune installed.

Just pull the negative battery cable for a few mins, should clear the code, else bite the bullet and do a PCM reset.

Re: Why are you not supposed to PCM reset if tuned?

Posted: Thu May 16, 2019 10:15 pm
by sragsdill
UPDATE: PROBLEM SOLVED. I'M LEAVING MY ORIGINAL POST FOR THOSE SEARCHING THE SAME ISSUE. I SOLVED IT BY UPDATING TO FORSCAN VERSION 2.322. IT NOW INCLUDES A "TCM RELEARN" OPTION. I HAD TO RUN BOTH THE PCM RELEARN AND THE TCM RELEARN TO GET THE DTC TO GO AWAY.

ORIGINAL POST:
Please help. I can't get rid of the wrench after changing BCM 726-12-01 to 09E7 (was 09AC). Speedo is right on the money though. I have researched all the forums, run the Module Initialization/Relearn function several times, tried to delete the TCM DTC P160A multiple times. No other DTCs exist. This is a very persistent wrench.

Vehicle info: 2018 F150 Lariat, 3.5L Ecoboost Screw, FX4, 3.55 diff, new LT275/70R18 Michelin Defender LTX M/S tires.