Random commanded AFR

[smokeshow]

So, I'm not an expert HP Tuners user, but I've tuned a number of vehicles and this problem has had me stumped for a while. I've been helping a friend with his tune and have been seeing some crazy commanded AFR numbers randomly dropped into the mix. Sometimes it will go to 16:1, sometimes 13.61:1. The latter isn't a PE number, and the former certainly isn't anything I would ever use.

I dealt with it several months ago while he was NA, and one day he changed his spark plugs and it somehow went away. Last week while tuning it for the turbo, it popped up for a split second but went away and never came back. Tonight while riding around with him, as the engine got into boost, that random AFR popped up again. I didn't have my laptop hooked up at the time but the WB gauge was reading mid 13s.

Now having boost in the mix makes this even more of a problem... I've beat this to death with no conclusion. My only thought is its a dying ECM, or at the least just a problematic ECM causing these issues.

Here is a picture of this stuff in action..




Would really appreciate some insight on this!

[98Camarod]

What ect does it occur at?

[Atomic]

Mine does that same thing occasionally....never figured it out though.

[smokeshow]

What ect does it occur at?

Operating temp, 178° F.

Mine does that same thing occasionally....never figured it out though.

Is it the same values, 13.6 and 16?

[SSUte01]

Sounds like the rear Cat Tests that many of the later models do.

[smokeshow]

COT and lean cruise are both disabled :/

[Iam Broke]

How about disabling all of the rear 02 codes to see if that solves it?

[smokeshow]

All of the "sensor 2" codes are set to no error reported. Am I missing some of them somehow?

[smokeshow]

Considering Atomic has had the same problem, could this be strictly ECM/OS related? Surely something like this can't have gone unnoticed.

[Twitch]

Add me to the list, although I haven't seen it under boost. Very random, but seems to happen when cruising at low RPM. Commands 16:1
COT and rear O2s are disabled.

[joshmith]

Smoke...Im guessing you've physically removed the rear o2's?...my 06 does the same thing finally had to reinstall them, absolutely can not get around it in the tune.

[Nitroused383]

Make sure you're not exceeding the maximum tps voltage.

[kjhallex]

Make sure you're not exceeding the maximum tps voltage.

This!

[axekick]

I have the exact same problem. I even emailed support but they were not interested in figuring it out. I am pretty sure its a catalyst test. The gen IVs have a setting to disable that but ours don't have it. At least not in HPT.

[smokeshow]

Smoke...Im guessing you've physically removed the rear o2's?...my 06 does the same thing finally had to reinstall them, absolutely can not get around it in the tune.

This is definitely the fix. All tunes I have seen that suffer from this are P59 PCMs. Its some catalytic converter loading check that changes the AFR, but it goes nuts without the rear O2s plugged in. The simplest fix is just to plug them back in and tie them up out of the way.

[CancerJCC]

Add me to the list, although I haven't seen it under boost. Very random, but seems to happen when cruising at low RPM. Commands 16:1
COT and rear O2s are disabled.

Instead of having your rear O2's set to "3 - No error reported" and the SES box unchecked set them all to "2- No MIL Light" with the SES box unchecked. I read another post somewhere and this took care of it for me. I also would get 16.00 commanded at low RPM. The other poster said it had to do with lean cruise.

For you other guys this might work as well but I know for sure Tony and I share the same PCM's.

[Twitch]

Good to know. I'll try it when I get my laptop back.

[Twitch]

Instead of having your rear O2's set to "3 - No error reported" and the SES box unchecked set them all to "2- No MIL Light" with the SES box unchecked. I read another post somewhere and this took care of it for me. I also would get 16.00 commanded at low RPM. The other poster said it had to do with lean cruise.

For you other guys this might work as well but I know for sure Tony and I share the same PCM's.

Did this 2-3 weeks ago. AFR has been steady since then.
I was surprised all the DTC tests still showed complete. Win/Win