Nine Ball

iTrader: (38)

I remember in the old days, prior to having custom tuning available, we used to pull the "PCM Bat" fuse under the hood and it would 'reset' things, sometimes causing us to run quicker on the next pass down the dragstrip.

Anyone know off hand what that fuse is for? Also, should I still be able to read/flash a PCM if it is removed? I'm having some quirky wiring issue with a car, all of my lights stay on if I leave that fuse in, and my ignition switch doesn't do anything. I pull the fuse, and my lights go off and the ign switch works again, and I can turn the lights on/off like normal. I even could read and flash the PCM with that fuse removed.

weird stuff.

xaon

iTrader: (12)

when I disected the harness in my car, the PCM Bat fuse was a direct constant 12v supply to the PCM. Unfortunately, other than that I don't know too much about it... there were a couple of constant 12v wires that went to different pins of the PCM, and several ignition 12v wires that went to the PCM.

Nine Ball

iTrader: (38)

does anyone know if the car will start/run with the PCM bat fuse pulled? I can't check that right now because I have the exhaust system and headers off the car

horist

I'll check today at lunch


I'm thinking it would work , just PCM would rely on default values... but I'll check

SmokingWS6

iTrader: (1)

The bat fuse is like the backup battery in your alarm clock. I've never tried to run or flash it while removed.

It almost sounds like you have a wiring/grounding issue. I've seen loose grounds cause all sorts of issues. Low batteries can also cause odd faults.

dummer

Sounds like the PCM is toast to me. Which car is this on?
Will it start up and run?
You're not using LS1edit, are you ??
If it's the '98, the PCM can get a checksum error stored, and , even though it will seem to program normally, it won't ever work again. That's what happened to mine. I even sent it Jesse Bub to have the PCM recovered, it still would not work.

Nine Ball

iTrader: (38)

The car flashed and started up just fine yesterday, with the PCM bat fuse removed. Not sure what the fuse is for, but the car runs like normal without it. weird

SmokingWS6

iTrader: (1)

It probably does not remember fuel trims and idle trims ect after each drive cycle. If the car is tuned properly it should not make that much of a difference anyway.