Hello thirdgen tuning community,
It seems like there is a lot of knowledge here so maybe someone will be able to recognize my problem.

I am running a 93 LT1/T56 and 16159278 ECM. I use TunerPro RT v4.14 to datalog and burn chips via the Moates PROM. Since I initially tuned it a few years ago it has been running great but it has never strayed outside of BLM cell numbers 16, 17, or 18 (for idle, DFCO, and open loop respectively). I was still able to dial in the VE tables to keep the BLMs in line.

BLM Cell RPM Boundaries: Hi=2600, Mid=1800, Lo=1200
BLM Cell MAP Boundaries: Hi=80, Mid=60, Lo=40
(even though they're very close, I also tried the stock values here)

So my question is: when the ECM is indicating a closed loop condition (with O2 sensors active, "learn mode" enabled, and BLMs updating) what could be keeping me from entering BLM cells 0 thru 15?

It seems like a long-shot, but I am beginning to suspect there is a flag or switch that needs to be set for one of the seemingly unrelated sensors that I am no longer using (egr, purge, etc...) to somehow enable the closed loop cells.

I have attached a compressed folder containing my current XDF ($DA3.xdf), BIN (Current_Tune.bin), ADS (My_LT1_Datastream_D.ads), a short datalog ADL (Current_Tune.adl) and some reference code text files.
The XDF, and ADS can obviously be viewed in Notepad or Wordpad but the ADL and BIN need to open with TunerPro or similar. I can also produce a TTS Datamaster log if it would help.

I feel pretty comfortable with the hardware, software, and theories but I am missing something huge here!

 

Any thoughts? Or, as a last resort, any GM tuning gurus that you think I could ask?
Thanks!

 

Did you ever get an answer to your question? I have the same problem now.