Custom O.S #3 Update for 2003+

[GMPX]

There was a problem identified in the custom O.S#3 for all 2003+ vehicles that was causing the ECT enrichment table to have no effect on final commanded AFR's when cold. This has been fixed and the updated .tun files are available by downoading the zip file shown below.

1 - Download zip file.
2 - Extract into the folder you store your tune files.
3 - Choose the custom O.S to match your exisiting tune (these new ones have a 'c' at the end of the file name).
4 - Full flash PCM.
5 - Calibration only flash the PCM with your existing calibrations.
6 - Alter ECT fuel table as required.

Updated Custom OS file link (5.05Mb) - CLICK HERE

Cheers,
Ross

[AGRO]

There was a problem identified in the custom O.S#3 for all 2003+ vehicles that was causing the ECT enrichment table to have no effect on final commanded AFR's when cold. This has been fixed and the updated .tun files are available by downoading the zip file shown Ross

Ross, this the exact problem i have, originally had 04140003, then i flashed cos 04140003c, it made no difference, the other problem i have is when i first start the engine (hot or cold) it runs extremely lean, like 22:1 afr! (wideband) while it is running lean the commanded afr is reading 14.63 yet it is still lean, its lean on idle and wot.after a some time the engine is running the actual afr changes back to where it should be,when i first start the engine, the command afr reads about 13.7 then gradually changes to 14.63, (after start enrichment) but still runs severly lean.please help :cry:

[Garry]

Does this problem appear in #5 too?

[BlackGMC]

Is this fix still required for 03+? The thread was started over a year ago, just wondering if it was incorporated into the OS or what?

[joecar]

I do believe the fix is still required for 03+ COS3...

and since there is no 03+ COS5, the problem does not appear in COS5 (I haven't seen this problem in 02020005).

[BlackGMC]

Thanks! So basically I do the same thing I did before but I use this new file instead of the one loaded into the Custom OS folder?

[joecar]

Thanks! So basically I do the same thing I did before but I use this new file instead of the one loaded into the Custom OS folder?

That's correct.

[Chevy366]

Wait a minute , I asked about this issue many moons ago and was told that the COS files had been updated to reflect the "c" correction .

[BlackGMC]

Wait a minute , I asked about this issue many moons ago and was told that the COS files had been updated to reflect the "c" correction .

Hmmmm, is this correct or is the earlier post????

[Chevy366]

Hmmmm, is this correct or is the earlier post????

Hmmm , would like to know as well , because I did a tune with MAF just to see if there was any difference and re-flashed without the "c" file .
Would think that this issue is over a year old that it would have been added by now , 7.4 or so !

GMPX , Ross any input .