A Dilemma - PCM Swap

[Mainous]

I have a problem that I would like some input on. I installed a Heath PCM in my truck last year and am very pleased with the way it has performed. Problem comes in that I took the truck for it's bi-annual emissions check yesterday and it failed. The way they test the 8600 GVW trucks in Ohio is a simple opacity test where they stab the throttle from idle up to about 3000 RPM. I only have about 30K miles on my engine combination so I know everything is healthy and the PCM is the only thing I have changed since the last emissions check.
I also own a fully stock 99 Burb with identical drivetrain to my 97 truck. I am contemplating swapping the PCM between the vehicles just long enough to pass the emissions test. I know I have seen others discuss swapping in "junkyard" PCM's on the forum. Can anyone tell me what troubles I am likely to run into when I swap PCM's.
I have a call into Bill Heath but thought I would throw it out to the group. What aggravates me the most is that Ohio is getting rid of their emissions testing as of 1/1/2006.

[tom.mcinerney]

tbogemirep , JD/GMCTD , and i think Black65/Billman , have posted relevant info--that is , concerning the PCM- swapping considerations.

Turbovair had to pass a similar test last winter, and passed readily following replacement of high-Mi injectors , and some other advive.
see, maybe:
http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=008115

I'd suggest a hard run (hot, after warmup) with 5-30 minutes at or near the test rpms to blow out soot beforehand....and it's a good bet that factory/OEM timing would be set for near minimum emissions.

[Billman]

You can not swap a '99 PCM into a '97 truck. One word - Passlock. Your '99 has it, the '97 doesn't.

I tried that myself. Found a junkyard PCM, had it flashed to '00 specs, installed, and No-Start. Then I went the Performance ECM Route.

When I test diesel trucks at the shop with the opacity meter, I perform 'clean-out snaps' as they're called to help a bit. Just rap the truck to help clean it out right before testing begins. Warming it up like Tom Mac says is also a priority.

If your interested, I've got the Original PCM that my truck came with. The Junkyard PCM I had flashed was sent as a core. I don't know if it's 100%, because I had a intermittent short that I blamed on the PCM. Over 1 year with the new one and it hasn't happened again. If you would like to try it, let me know.

[Mainous]

Billman,

The test snaps that you mention are exactly how they are testing the truck for emissions. I would be ok if they tested at a fixed RPM, but when they snap the throttle and then let off, the turbo doesn't have time to spool up to burn the additional fuel that the PCM is delivering. Not to mention the fact that they are doing it in park.

I am definitely intersted in your spare PCM. Are you wanting to sell it, or can I just rent it from you? You mention a short of some kind. I just need it to last for about an hour. Long enough to get me to and from the test facility. Drop me an email with your phone number and I will give you a call.

mainous@cinci.rr.com

Thanks!

[rjschoolcraft]

Kennedy had a 99 pcm in his 96 truck.

[Billman]

JK had it in his '96 w/extensive work to the steering column and/or his connections with someone at GM.

Diesel6.5 has also done it. Too much work for me. Performance PCM blows it away as far as I'm concerned.

Jeff - I don't think you'll get too much boost in Park/Nuetral. Here in NY, they test over 10k GVW. Your Performance PCM is probably doing you in w/~80mm of fuel.

My spare PCM/ECM is here for you to use. I wanted to keep it for similar encounter someday. I also wanted to re-install to verify original problem. Haven't done it yet. Pay for shipping. Return it when you're done. It has to be an exact match. Bring plenty of 20amp fuses for the ECM-B port. That's what it kept blowing. Sometimes 3 fuses in 10 minutes, other times it took weeks.

Check your e-mail...

[Billman]

Now I see your sig and you have 4X4.

I'm 2wd.

Not sure if it will work.

It's here to try, your call...

[autocrosser]

Though I would make a comment on the last post about the ECM fuses blowing. I had that happen about 4 years ago and after putting another in it worked fine. I put a 10a fuse in later and it ran for several months ok. I then put the 20a fuse in and it ran until last month when it blew two of them. I put a 25a in place of it and later changed it back to a 20a amd it's fine now.

The PCM that it blew in the second time is a different one as I have a Heath PCM in it now and kept the original for a backup.

There must be a intermittant problem that occurs sometimes that causes them to blow. Anyone else had this problem

[Turbine Doc]

Bill I've run a 96 PCM in my 98 so all I can say is that it MAY be possible, I don't know why it worked in mine, one thought as I was typing the reply, the 96 PCM I installed had been reflashed to a early) Z Industries tune(lame stock F had as much guts as that reflash).

Jeff Go to one of the various web sites if you can't find one from a member here $75 is what I paid for my last junkyard one I used for a core for reflashing. just so I could have my styock one for the situation you find yourself in.

[Billman]

Tim - Did you ever verify if your '98 has Passlock?

[Turbine Doc]

Yes it's there it won't start unless I do the pass on the swapped PCM, once learned no problem, only odd ball is the 96 Z ind reflash I got from JK long time back, and one PCM from Heath that did not require the learn, I plug them in & try them 1st to see if the learn needs to take place.

I've run about 5 different PCMs through my truck now with stock & different tweaked performance maps.

I have a 2wd PCM I got from Mark Rinker I've yet to try in mine; more as and experiment to see if a 2wd will work in a 4 wd truck rather than something I'll run, it was going to be a core for somebody in Germany that wanted to reflash but backed out so I have an extra PCM to play with.

[Mainous]

I received Billman's PCM today in the mail. Immediately swapped it in and had no initial problems. Main concern was with the mismatch of my truck being 4WD. I had no issues here. Ran the truck to the testing station. Made a couple of full throttle runs before getting there. The truck skipped a bit during hard acceleration likely due to not having run a TDC learn with the new computer(my truck is set at -1.94). The truck tested at 0% opacity just as it did on my original PCM.

Billy,

It didn't blow any fuses. I know you were hoping it would show some symptom. I will get this headed back to you in tomorrow's mail. I can't thank you enough. You made what could have been a difficult problem very easy for me.

[Kennedy]

Originally posted by ronniejoe:
Kennedy had a 99 pcm in his 96 truck. The 99 pcm was a salvage unit that came with the 99 van engine that I bought. It was a special neutered unit w/o a VIN etc from GM testing and development.

Wbuchak installed a later steering column in his 97 to get a 99 program to run.

[Billman]

Jeff - Glad to hear it worked out for you.

Too bad it couldn't verify my diagnosis.

[MikeC]

Jeff,

Sorry I didn't see this sooner. I live S.E. of Columbus and also have a stock 96 PCM. If you need it for your next test just let me know.

Also, my Suburban is in having some minor body work done and then will be for sale. Unless the new owner would happen to want it the PCM will be available. I only removed it to put in a reflashed unit.

Mike

[Mainous]

MikeC,

Drop me an email when you are ready to turn loose of that PCM (mainous@cinci.rr.com). Also, if you find that you aren't recouping the dollars for some of your modifications, or the buyer could care less,I would be interested in some of those as well.

Thanks

[diesel65]

To get the Passlock to work in my 97' took more than swaping the steering column.

I had to replace the EVO module, located under the radio. Change the connector shell that plugs into the module (allow more wires) and fabricate a mini wire harness to connect module to the steering column and tie in the instrument cluster to work the security light.
I also had to find the various terminals that go into the connectors.

The 97 computer will work in the 99 because it wasn't programmed to recognize the EVO/Passlock signal.

[moondoggie]

Good Day!

I wonder if it might not be easier next time to leave your PCM alone, do all the other above-listed stuff (fully warmed-up, a few hammer-down runs), then simply stop a couple blocks from the testing station & hook your vacuum pump straight to your wastegate actuator. This would make sure the wastegate was fully closed, so the turbo would spool-up as quickly as it is possible for it to do so.

If doing this provides enough air to pass the opacity test, it seems like it would be a lot simpler than the other ideas presented. If memory servers, JK told me the stock PCM in my 95