Code 55 Lean Condition at WOT

[Paul Workman]

Dom,

What are columns G and H? Are they LEFT and RIGHT injector current, by chance? If it is current, it raises an interesting question.

Also, would it be possible to remove the label that obscures column "V"? I suspect RIGHT PW is relatively the same as LEFT PW. but I'd like to see that to be sure, as the label covers the PW at a critical point.

p.

[XfireZ51]

Todd,

If you look at the scan, the timing went to 20d even tho the Port Throttle was still open. All of the mechanical bits for the secondary are in there. I removed the throttle plates only. Again, looking at the scan, you'll also see that the secondary MAP signal was more than adequate for maintaining the port throttles open. Its not an issue with the port throttle logic or mechanism. I thought it may have been when I first saw the SES light.
My thought was there may be something wrong with the timing which then caused the ECM to throttle back the injectors

[nowa]

Hi @All

column J Is this your MAP sensor voltage ? If it is I think its too low @wot. It should be 4,88 V, not 4,33 V ( MAP 4,3 V -> ECM less fuel -> code 55 ? ).

norbert

[XfireZ51]

Originally Posted by nowa

Hi @All

column J Is this your MAP sensor voltage ? If it is I think its too low @wot. It should be 4,88 V, not 4,33 V ( MAP 4,3 V -> ECM less fuel -> code 55 ? ).

norbert

Norbert,

Column J is the TPS voltage. And Column AB is TPS%. MAP is column R.

[nowa]

ok I messed up. You got 4,33 V tps-Voltage before and after the shift. So its not the cause of the problem.

Another theory. Column M shows knock retards ? All over the visible rpm-range ? Whats the strategy of our ECM to prevent/recover from exessive knocks ? (Todd: ECM permanently removes 5d of spark advance when persist knock is detected) Are your new sparkplugs the cause of detonation because they are too hot ?

norbert

[tpepmeie]

Originally Posted by nowa

(Todd: ECM permanently removes 5d of spark advance when persist knock is detected)
norbert

Norbert, where did you dig that up? I must have said it in a previous thread. Anyway, that comment was in reference to Low Octane Knock retard, which is not what Dom is experiencing. His is the usual short-term high load knock event. This would not trigger the Low Octane activity.

Dom, the trigger for a Code 55 is a lean O2 reading during power enrichment. This means lean side of the "set-point" in the calibration. My theory is the 55 set, then the secondary injectors shut down (as they are supposed to). That put you into the PT closed VE & spark tables, which is obvious from the pulsewidth change after the code.

because the port throttle plates are gone, the airflow remained high. The O2 readings after the shift are absurdly low, indicating a real lean condition.

Best to get out the FSM and troubleshoot the 55, before tearing into the calibration.

Todd

[XfireZ51]

Todd,

It isn 't my thinking that its something in the calibration. I was only wondering what if anything in the logic might explain the ECM commanding
a lower PW and SA the way it seems to be doing here. I'm not sure if the lower timing is causing the ECM to command a smaller PW or vice versa.
I have looked at the FSM and it basically is pointing to the Fuel System.
We looked at FPressure this weekend and with primary pump fuse out, FP spiked to 48psi and then settled to 42, and the same numbers with both
Primary and Secondary pumps working at key on. I've borrowed an FP gauge with a long hose so as to tape gauge on windshield and will check out pressure with car rolling and at WOT.
My question is if there was a loss in fuel pressure, would that cause the ECM to command a smaller PW? At this point, I would be at a loss to explain how. I'll keep you posted.

[XfireZ51]

Todd,

On Fuel Kill, can you explain RPM/MPH Upper/Lower Error params? Is that the hysteresis? In my bin its set at 2800+rpm.

[tpepmeie]

Not following, Dom. Don't recognize those parameters.

[XfireZ51]

Originally Posted by tpepmeie

Not following, Dom. Don't recognize those parameters.

You'll find them starting at 614 and going thru 61D. If you could review the hack for the $D0A def, that would help. Here's another question to contemplate. Could it be that the code was written as to ignore the cause of the malf? So even if the ECM was the cause of the lean exhaust,
it would still set a code 55? Or if Fuel Cutoff, then ECM should ignore the Lean Exhaust?
My gut tells me GM would play it safe and not bypass the malf flag even tho it was a previous ECM action that caused the malf in the first place.