The Stovebolt Site Forums The Shop Area The HiPo Shop Donor vehicle emissions wiring/programming questions

I am working on the wiring for my project, the donor vehicle is a 2001 chevy 3500 cutaway van with an 8.1 and 4L80E . I would like to use the oem computer and most of the wiring. Can I eliminate the catalytic converters,, and what else can I get rid of? I tried calling a place that offers pcm flashing and they only do oem specs. I would like any and all advice!

I got the Chevy schematic thumb drive for this vehicle and with YouTube help I now have the wiring figured out pretty much but this computer thing has me by the A--. Dave

If the OEM exhaust has pre and post oxy sensors, you will have issues when you remove the converters. It probably will run ok if the OEM system had only pre converter sensors.

To trick the computer into not knowing you’ve bypassed the catalytic converter in a setup with a post cat. Sensor you could try using an oxygen sensor spacer
You could make your own or just buy one online
See attached photo
Offsetting the sensor back out of the exhaust flow will change its output just right
I’ve had success using this on early 2000s beater cars for farm use after the catalytic converter collapsed internally and had to be removed to prevent back pressure on exhaust.

If using the OEM computer gets problematic, here's another possibility:

www.ampefi.com/product/ampefi-transmission-controller-with-4l80e-subharness/

I don't have any hands-on experience with this product, but I'm considering using a 4L60E trans and a small block V8 on an upcoming upgrade to a mid-1990s S-10 pickup that's currently running a 4.3L V6 and a 700R4 trans. The same company makes a trans controller for that application.

A friend uses a piece of black electrical tape over the check engine light on his truck. It masks the light for the issue he has because of modifications, but also masks the check engine light for ALL issues. Not saying I'd recommend that, but....

Your probably barking up the wrong tree by asking the dealer about your PCM

If I understand the 8.1L, it uses the same reluctor wheel, coil on plug and cam sensor that the LS motors use. I shouldn't be much of a problem to edit out the cats and make your nuisance CELs go away. If it has VATS that can be edited out too.

I'd start by looking for a local tuner that has the LS1Edit or HPTuner software. Any shop with an engine dyno will have a list of tuners that use their facilities and tell you which ones tune GM engines (if they don't have it themselves).

There's plenty of mail-order tuners too. Texas Speed and Marine comes to mind and I've used them a few times for LS engines. Just search "mail order tune 8.1" on Google to find ones that'll do the 8.1 PCM. Most of these places have an order sheet that will tell you what they can edit, including the cats.

If you're confident about your wiring harness stand-alone modifications, you may not need it, but LT1tech.com has some useful instructions on how to modify LS-style harnesses. He also does mail order tuning and it'd be worth asking him about the 8.1. His name is Brandon.

Yea dealer has no clue what your talking about and they dont even have software capabilities to do what you want/need. You can remove the cats no problem. All you need is 2 front O2 sensors and the MAF to make it run “correctly”. You can even run them no maf or 02’s and it will revert to the MAP tables and run fine but there will be no fuel trims and its not optimal but it does work. Ive used it both ways on turbo builds. I will 2nd vote Brandon from LT1swap.com to hook you up with whatever you need. I own HP tuners software and have used it on all my builds and friends builds but I did have him flash a few for me a long time ago and he was great to deal with. I bought the software to do it myself just for ease of modifying and sometimes unexpected codes will pop up and you can basically tell the ecu to not monitor them. That ecu is super archaic by design. I would almost compare it to a carburetor of my generation hahaha. You can just tell it to ignore literally everything and it’s totally fine. As long as its got power/ground/ no VATS issues then its more than happy to run everything.

Whats wrong with running Cats? The modern ones don't hurt the power output like the early ones did, plus cleaning up the exhaust never hurts.

I have no issue with leaving the cats, in fact I have not removed them from the exhaust yet. I did not go to a dealer for flashing I called a tuner and they only went to oem specs. I am now going to contact the folks that were recommended by you guys. Dave

I just called the folks, the guy is in the hospital for a few days but will call me when back at work. Sounds like I may have called the right folks. Thanks guys! Dave

As I modernize my Enterprise, I'm plumbing fuel and EVAP lines into the tank in advance. It's easy enough to find a carbon can from an old GM vehicle, the early ones were just vacuum actuated from the engine so no computer needed. I've welded O2 sensor bungs into the new pipes, I can plug them til needed.

Doing the homework now, so if I get ambitious and decide to go full modern on the engine controls, the basics will already be there. And heck, it'll even do the planet a little bit of a good turn by capturing all those excess hydrocarbon emissions. I'm not putting the smog pump back on the swapped Cadillac V8 tho :-D