Getting STFTs, no LTFTs

[jclayc]

2005 LS6 CTS-V with heads/cam/intake

I'm very new with hptuners but have a few knowledgeable people helping me out. I know you don't have to have LTFTs to tune but I'm having trouble with always getting 0s for LTFT but getting readings for STFTs. Overall, my issue is an intermittent dip and bounce in the idle when coming off heavy gas. I think that's related to my injector tuning but I want to eliminate o2 issues as the cause and no LTFTs is making me think I have something up with my o2s.

Oversimplifying but - everything I've read says getting LTFTs is based on reaching specified ECT and MAP pressure (which I'm reaching) and having good o2s (which are oscillating fine but I replaced them anyway & tested the wiring back to the PCM every way I know how). I've also read having an exhaust leak will prevent LTFTs but I can't find a leak. I thought maybe it's something bad in the PCM/ECU so I swapped in another I had. Same issue. Here's the first tune I tried.

base.hpl05v_base.hpt

You may look and see the STFTs are right around -1 and maybe LTFTs just aren't supposed to be anything but zero. Well, I friend gave me a "start over" tune that sends STFTs up into the 20s-30s (with instructions not to push it above 50% throttle with this tune) and should cause LTFTs to kick in. I also "forced" Closed Loop in VCM Scanner. That tune and log is below and still no LTFTs.

Base 1.hptpost-base1.hpl

Am I getting STFTs because STFT Open Loop is enabled - and I'm not getting LTFTs because I'm truly in open loop?

Thanks in advance for your thoughts!

[mowton]

Check and make sure you do not have any DTC's (pending, history etc) that could force open loop....most likely O2 related. Maybe the mil was just disable? You can read the dtcs with the keyon and throught the scanner (engine icon). Did you try and set the trim learn as well in the VCM?

Ed M

[jclayc]

Nope, no DTCs (to test, I pulled the plug on the o2s and got DTCs. When I plugged them back in again, they stayed clear). And, yes, I forced fuel trim learn on the same time I forced Closed Loop on.

In case it's something with the o2 wiring, I tested all wires back to the PCM for resistance, continuity, short to positive and short to ground. They were all continuous and had like 0.3 ohm resistance. No short to positive. I'm not sure how to interpret what I got for a short to ground. Two wires gave me 12v, one gave me like 11.75. Another showed nothing. I think that's checking out as ok - two (+), one low ref (-) and one ground.

[silverado08]

i had problems lately with my scanner not picking up ltft it was because the config magically changed and quit reading i had to redo my main scan table to make it read again.

[jclayc]

what you you mean redo your main scan table? delete ltfts and add them back again?

[jclayc]

thanks to coloradospeed (coSPEED2 in the ls1tech.com forum), this problem is solved.

It was so strange having STFTs, no O2 codes and all wires from the O2s to the PCM testing fine that coSPEED2 suggested I take the car to a GM dealer and have them re-flash the computer back to the latest OS. That was it. I've got LTFTs again and can start tuning in earnest.

coSPEED2 has been beyond great in helping me with this issue and tuning in general. I'll buy my parts through them from now on

[mowton]

thanks to coloradospeed (coSPEED2 in the ls1tech.com forum), this problem is solved.

It was so strange having STFTs, no O2 codes and all wires from the O2s to the PCM testing fine that coSPEED2 suggested I take the car to a GM dealer and have them re-flash the computer back to the latest OS. That was it. I've got LTFTs again and can start tuning in earnest.

coSPEED2 has been beyond great in helping me with this issue and tuning in general. I'll buy my parts through them from now on

Wow, thats one for the books. A corrupt OS.....thanks for sharing the final solution.

Ed M

[jclayc]

totally discouraged - LTFTs are back at 0 all the time. I can only think I've got some sort of electrical problem: a short or bad ground or something, even though my (limited) tests can't find anything.

[jclayc]

I put a whole new ECU in the car and modified the stock flash instead of applying any existing flash file I have. A few days and like 6-8 runs later, I still have LTFTs so that's good. I also replaced my 60lb Dekas with 42lb Deatschwerks injectors. I think I have the right info in the tune for them.

With LTFTs to use with the STFTs, I'm now tweaking the VE table to try to get fuel trims where they should be. Any thoughts on the attached?062115-afterVE2.hpl05v_062115_v2.hpt