I do not know if the TBI PCM can be used to run the TPI, but I do not think so. Based on my research, I would say no, but that was before I found thirdgen.org. Someone here may be able to tell you how to do it. I just did that exact same swap, but used a separate ECM to run the TPI system.
Here is a
link to my website documenting what I did. Here is the
link to my experience tuning the TPI for the Suburban. I am using hardware and software available at
www.moates.net.
I ran a separate computer to run the TPI and left the TBI PCM in to control the 4L60E and anti-lock brakes. You will need to jump three aspects from the TPI to input information to the original PCM to drive the 4L60E. The harness I bought from Street & Performance included these jumpers. You can see it
here. (See item #31). I think you could accomplish the same thing by simply making your own splices with a new TPI harness to the original TBI harness. One connection between the TPS (blue wire), one between the distributor (purple wire), and finally three to the original MAP sensor connection. You may even be able to run a second MAP sensor specifically for the original TBI PCM.
If I had it to do again, I would have found a cheaper place to buy my ECM (I used a #727 under the hood), harness and MEMCAL. Having done a lot of research on this board, I could have probably saved $500 in ECM, harness and MEMCAL parts alone. For the price of a "custom" S&P chip, I could have bought equipment to burn my own. In fact, that is what I am doing now. I had no choice, because I promise you, for a Suburban the AUJP bin needs a lot of timing taken out at the 60-100 kPa ranges. And the "custom" S&P chip is nothing more than a tweaked stock AUJP bin (a little more timing and VE at the top end). "Custom" is a joke!
Also, you will need a VSS signal to the TPI ECM (if you go that route). The VSS in your Suburban kicks out like 128,000 ppm. You need to cut it down to the 4000 ppm the TPI computer needs. I tried just tapping into buffered signals for the cruise control and original PCM, but could not seem to make it work. So I ended up getting a
Dakota Digital SGI-5 interface box (application #3 in the manual), but still have a few bugs to work out (interference signals). Without the VSS, you will not have EGR, CCP, and the idle is affected. It will also want to stall when stopping because the DFCO does not know that you are should be in decel mode, so the BLM drop big time, which I think causes the engine to stall. But there are probably a few other factors that play into it a well.
Good luck and please E-mail me with any questions. Ed
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