Resetting PCM

bcfitzsimons · August 21, 2003

Everyone-

I was reading about how, with a Westers PCM, you can force the computer to "relearn" timing/fuel curves for your engine by doing a "battery disconnect/cold startup with idle to warm/put in Drive and hold truck in place with the brake" drill. Does this reset and relearn procedure work with the stock PCM too? Is there any way that you can force the stock PCM to relearn timing and fuel injection parameters without reprogramming the PCM?

Thanks-Fitz

CMNTMXR81 · August 22, 2003

It only sets it back to GM's conservative base curves. From there you are supposed to run/drive the vehicle through a series of tasks to help it learn properly. These can be found on www.OBDII.com.

There is little to be gained performance wise out of this other than clearing the PCM of any goofy cobwebs in it's programming that it's learned from your driving style.

bcfitzsimons · August 22, 2003

CMNT-I figured that I'd at least try it because since the weather's been so hot, my truck needs 91 octane to prevent any pinging. If it can "relearn" on 89, then I'll save some $ at the pump (considering premium's at $1.89 here now).

Will the Wester's "learn" procedure work for the stock PCM?

Fitz.

CMNTMXR81 · August 22, 2003

Well, it does do good actually aside from shutting off the SES light if you have it on.

You see, the PCM learns or should I say "adapts" it's fuel and timing curves to your driving style. It learns how you accelerate, decelerate, loads, do you drive with the A/C compressor on all the time, etc, etc.

By resetting the PCM to it's base "safe" and conservative curves then going through that "idle relearn" as it's technically called it'll clear out many of those cobwebs that I mentioned previously.

bcfitzsimons · August 22, 2003

Sweet. I'll try it this weekend and see how it works. How long do you need to have the battery disconnected before the PCM resets itself?

Fitz

greyghost03 · August 23, 2003

Sweet. I'll try it this weekend and see how it works. How long do you need to have the battery disconnected before the PCM resets itself?

Fitz

I think you have to leave it disconnected for at least 10 min to reset it. You can leave it disconnected longer just to make sure!

JimWilson · August 25, 2003

1/2 an hour seems to work best for me. After you reconnect the battery drive it like you stole it for about 100 miles -- around town and on the highway -- and it should be a bit "smarter".

CMNTMXR81 · August 25, 2003

10 minutes to a half hour! You guys sure got a lot of time on your hands.

usually 1-2 minutes at most is sufficient.

bcfitzsimons · August 25, 2003

2 minutes, 5 minutes, 30 minutes-I guess what I'll do is just disconnect the battery and leave it disconnected for the same amount of time that it takes me to drink one bottle of Bud.

Fitz

JimWilson · August 28, 2003

10 minutes to a half hour! You guys sure got a lot of time on your hands.

usually 1-2 minutes at most is sufficient.

1-2 minutes? Geez, you sure drink your beer faster then I do...

CMNTMXR81 · August 28, 2003

Why waste time, I've got 11 more to go.

bcfitzsimons · August 28, 2003

Well, Tuesday night I unplugged the battery, and changed the plugs out to new NGK TR6's. The old ones (only 10000 miles on them) were as white as ghosts, with black crud caked all around the outside threaded surface. Then I reconnected the battery and did the Westers' relearn sequence.

There is a definite noticeable difference. More responsiveness, and much less pinging (although that's probably from the new colder plugs alone). There's still a highway-speed part-throttle engine sound that's much softer than a ping, but still sounds like predetonation-it just doesn't sound as smooth as when I dump 92 octane into the tank. Maybe what I'm hearing is just increased airflow and combustion noise from dipping into the gas. Hard to say. Have to admit, though-it is way smoother with the new NGK plugs in it.

And it only took me 3 beers worth of time to change out the plugs and reset the computer-

Fitz