Changed OS Can't Enable PE

[Steve Bryant]

I've switched back from a custom OS and moved to the most modern standard OS that my truck can use (12212156). Here's what I've done so far:
Calibrated the VE table for Stoic (trucks are set @ 14.68 vs. 14.63 for cars BTW)
Calibrated the MAF (with {B0120} change over to go exclusively to MAF for 400 RPMs)
reset the MAF (with {B0120} change over to go exclusively to MAF for 4000 RPMs) & verified that setup will track stoic nicely to about 5,600 RPMs (here's where the problem starts)
Attempted to enable PE (see attached tune)
Commanded VE obediently goes to 12.0 (set as test value initially, see attached file) and WB02 (using PLX analog on Aux Voltalge input 1) gets worse rather than better when PE is commanded.
Please take a look at the image of the problem, the tune and the logged data. I realize that I also have a spark/KR issue that needs to be addressed. Note: this is for a 2000 Yukon XL with an LQ4, a 200/206 cam running 87 Octane. Everything about the stock truck tunes are set up to not use PE. Also, when PE was disabled, the MAF calibration was at least maintaining about 14.6:1 AFR.

Thanks to all,

Steve

PS: this boy needs help!

:help:

[WeathermanShawn]

Steve..

Excuse my ignorance on this one, but is the normal PE TPS Enabler B3616 supposed to be 90%?

I take it you are wanting to enable PE, but it does not? I am just wondering if that high of a TPS setting along with the fuel step size is a concern:unsure:.

Just a thought..

[Steve Bryant]

Shawn,
Thanks for your response. I first started with steps set at 0.020 (stock setting for this OS for a truck). That seemed to migrate the commanded AFR at a slow rate, so I found a 2002 Z06 Corvette tune (HoldenCrazy) and I copied and pasted all of the values from the Mixture Parameters from the Corvette tune into mine. On {B3616} 90% may be a little high. My thought was that I wouldn't want to have a rich mixture for pulling long mountain grades towing my 8,600 pound trailer. I did just now find one of my older OS tunes where I was able to successfully enable PE and that tune had {B3616} set at 65%. That tune included a Back Up VE table and did not have a step size parameter.

[joecar]

Steve, I would try doing a full flash again.

[Steve Bryant]

Joe, I'll try a full flash again. As an aside, my turck has two fuel tanks that each have a float type fuel level sensor. The PCM is picking up the level/percentage of each, but the PCM is not summing the two, only the primary tank . . . so maybe all of the bits are not in their proper 0/1 status. Another thing that I could try is to go back to my older OS tunes where PE did work properly and see if PE still works there, then do a full flash with this tune.

Thanks very much for your suggestion.
Steve

[joecar]

Steve, what was the original OS and what COS did it have prior to this OS...? Yes, give the older OS a try.

It may be possible that your PCM might not be compatible with this particular 12212156... having said that, look at tables G1206/G1207, I don't see any mention of fuel tanks in G1207, but maybe the value G1206 is significant beyond the values in G1207 (i.e. there may other features not mentioned in G1207)... this is just a guess on my part.

[Steve Bryant]

Joe, my original OS was 09381344. I thought that any of the other standard or custom operating systems for the 512 kb PCM's would work. I have flashed COS 01270002 and 01270003 in this PCM. I experienced some problems with the maintenance of stoicimetric AFR using 01270003, so I switched to the latest 512 kb standard OS that had been used on the 3/4 ton GMT800 series vehicles (among other things) which is why I choose 12212156. I'm also attaching my original factory tune.

Thanks again for your willingness to help!

Note, I could also have some sort of unmonitored failure of my PCM (self test checks of RAM & checksum come back OK). Also, reflashing the PCM (full flash) with the same tune has not borne any fruit yet. I'll try a full reflash with one of the older tunes where PE was successfully enabled (back about in 2005/6).

[wait4me]

B3644 needs to be moved to 1. That will make it add fuel faster

[Tordne]

Hi Steve,

The B3644 parameters Jesse mentions is in the 2002 OS (12212156) in case you're wondering why you can;t find it in the tune you attached.

One thing I noticed in the attached tune (Post #7) is that the B3608 (delay before entering PE Mode) value is set at 60 seconds. Have you tried setting that to 0?

[Steve Bryant]

Thanks everyone for the additional comments. The tune in post 7 was just to show what the original factory tune and OS were when I bought the truck (posted in relation to Joecar's comments). I have not used that tune for about five years.

I'll make two more posts to show some more details.

[Steve Bryant]

OS 12212156 has been flashed to the truck for a number of months. I believe that I have both the VE table (set up in SD only by failing the MAF) and MAF ({B0120} set for 400 RPMs) set up independently to track stoic pretty close. Here is the basic tune and a log plus a picture to illustrate this (at this point PE is delayed for 60 seconds to keep it out of the picture).

[Steve Bryant]

Here, I have changed B3643, B3644 and B3645 all to a value of 1 and the delay for PE is set to 0 seconds. The commanded AFR obeyed quickly, but the AFR did crazy things (tune and log included, see two pictures below, commanded AFR (green line) jumped right down to 13.0:1 then later right back to 14.68 when out of PE).

[Steve Bryant]

Right now, based on current symptoms I think that I have a partially defective PCM. Here's why.

I tried commanding an AFR of 13.0:1 using the BiDi controls and driving around. The commanded AFR jumps down to 13.0, but the WBO2 is no where near what is commanded. Also, my PCM will not include (add) the fuel from the aux tank into the displayed value on the fuel gage (even though it gets the proper voltage & A to D conversion as shown from logged data). I also had some crazy, inconsistent intermittant AFR problems on a long trip last winter when it was about 10 degrees F. The AFR could be around 14.6 and then suddenly jump to 16:1 for an hour on the WBO2 and it would set some codes for mixture too lean.

I'm about at the point of buying a replacement PCM as I no longer trust this one. It's more than just this PE issue which is frustrating enough. What do you think? Thanks in advance.

Steve

[WeathermanShawn]

Steve, your instincts are probably as good as anybody as to what is going on.

If it was just a PE issue, then I might suggest changing the TPS% Enablers to say 25-30% as a test. You could log FTC cells just to see what is happening as you 'enable' PE.

I have found PE Mode to be part 'voodoo' at times. I believe in the OS we are both using, that EVAP also becomes active during PE Mode. I had a dissimilar but equally frustrating issue when I attempted to set all PE TPS Enablers to 10%. I could not control Commanded AFR due to the excessive interference from the EVAP and its FTC Cell it 'shared' during PE.

You could always try a new PCM, but that is the only other thing I can suggest.

Let us know how it turns out.

[joecar]

It's hard to tell... sometimes the problem is solved by trying a new PCM.

[Chevy366]

Have you tried doing a "Full Flash" with your current .tun ?
Full Flash with the current .tun and see if it makes any difference .

[Steve Bryant]

Thanks to all who have responded. I'll try a few more things and get back with the results.

All my best,

Steve

[ScarabEpic22]

Hmmm interesting for sure, if you can pick up another PCM cheap and dont mind spending $100 on a license, that'd be my next step. You've done a TON of trouble-shooting and everything seems to point to a partially-defective PCM. Or if someone's local to you and already has their PCM licensed, full flash your tune into it and try that. Could even be a bug in the tune file itself, have you rebuilt the tune from a fresh 02 OS file with 0 modifications?

[Steve Bryant]

Erik,
I'm already in the process of doing what you suggest. I bought a used PCM at a salvage yard yesterday.

Thanks for your response!

Steve

[ScarabEpic22]

Let us know what happens Steve, troubleshooting a defective PCM when you've done a few other things gets to be a tedious process. But you sound like you're closing in quickly!

[Steve Bryant]

Thanks Erik,
I absolutely will keep you good folks posted. That way, everyone gets to learn from both my mistakes as well as occasional successes. That's one of the many beauties of a forum like this when used properly.

I probably won't work on this issue for a few days as I have some other things that I need to do first and it's 107 degrees F (42 Celsius) here today! :shock:

Steve

[Steve Bryant]

A brief update. I haven't worked yet with my replacement PCM (motherboard died on desktop computer and right side header broke at weld - very loud). Unrelated events, but both more pressing at the moment. Header resolved and replacement computer should be here in a couple of days. I'll now get to reload all applications and transfer all of my files & convert from WIN XP to Win 7 64 Bit).

I'll get back to the PE issue and let you good folks know what goes ASAP.

Steve

[ScarabEpic22]

Just built my new desktop from scratch, finally was able to order some modern components (Phenom II X6 1055T -> going to OC to 4ghz, 8gb ram, HD 5850 graphics, BluRay rom, 750w psu, W7 Ult x64) instead of my old Athlon XP machine. My laptop has been running W7 since public beta, its better than Vista for sure. After spending this summer working to upgrade the company's desktops to Windows 7 from XP on the same hardware (plus RAM in most cases), just make sure all your critical apps work on x64. Ive struggled with a few things like an ancient wireless adapter than Linksys never released a x64 driver for, but people have hacked other driver to make it work.

[Steve Bryant]

Synopsis: I did have a defective PCM! I should have followed my gut feeling a long time ago.

Details:
I can't believe that it has taken me so long to really start to get to the bottom of this. On Wednesday of this past week, my wife and a friend drove our Yukon XL on about a 150 mile trip. I had filled the vehicle with gas the evening before. The first half of the journey, everything seemed normal. On the return trip, the fuel gage went to dead empty and the low fuel warning came on. She filled the car up with gas and it still showed dead empty. I checked the fuel levels (there are two tanks on this vehicle) and both showed full using the EFILive Scan Tool and yet the gage still read empty.

This afternoon, I did a full flash of my replacement PCM and change the VIN with the BiDi control for that purpose. Even before I started the vehicle for the fist time with the replacement PCM (not new, bought from salvage yard) the fuel gage read full and there was no low fuel annunciation (sorry, I'm an avionics engineer and it's hard not to think in airplane). Then I took the car out on the highway and Power Enrichment works like a champ!!! It still needs to be dialed in, but it works great. In fact, I need to re-check speed density only and MAF only because the car runs richer in general than with the other computer. I've opened up the old PCM and I don't see anything obvious like evidence of an overheated power transistor or a bloated electrolytic capacitor.

So, long story short, I chased my tail like a crazy cat or dog for far too long. Not having the time to really devote to this issue and get it resolved has also been a big problem. Now, I really want to get things straightened out once and for all. I'll make at least one more post to this thread once I've got things tweaked in better for those who are interested.

Steve

[joecar]

Steve, good job that you finally narrowed in on it :cheers: ... PCM's don't usually go bad, so something may have happened to traumatize this one.

[RonC]

Steve, have you changed to 30# injectors as B4001 suggests? Just wondering.

Ron

[Steve Bryant]

RonC,
Yes, {B4001} is set to an injector flow rate of 3.773438 g/S (equates to 30 PPH) in all cells. I have the return type/constant pressure fuel system.

Steve

[ScarabEpic22]

Steve, glad you got to the root of your problem! Finally you can get your truck dialed in now!