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p0236 GL4 and ATT ??

M

mmcna

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Thru p0236 code tonight on the way home from fishing tonight.

After reading some previous threads it would seem that that should not happen with a GL4. I did run her pretty hard up to about 100 mph(gets there quick now). I never got this code with the GM-8 and TM, wondering why it is showing up now with the ATT????
 
High IAT will also trip that code. If it was warm out today the combination of the boost you were running and the IATs that were generated when you hit 100 caused the code.
 
It was between 65-70 deg.F I would not think that would cause high IAT's.
Maybe it would?

I do know there is more heat in the engine with the new injectors, temp gauge actually moved a little bit on the 100 mph run. Had not before any other time it ran that fast.

What is GL4 set at for overboost? Could the combo of the HO injectors and the ATT actually overboosted it?

This is an awesome machine with the mods that are currently done to it. I am very what caused this code I have never seen before.
 
Do you have a MAF sensor? Guess you can take the TM out of the sig.

what boost do you get with the ATT? Do you have a gauge? I would rather suspect underboost or a restricted air filter.
 
I just removed the turbomaster from my sig. Thanks I forgot to do that.

I do have a boost gauge. The max I see with the ATT is 12, that is full throttle.
Cruising usually only 1-2 psi. on flat roads. Can it be under boosted?
 
Is there a MAF on 99 suburbans on the air filter/intake tube? see if air filter is dirty or something restrictive in the fender or whatever.
 
I would look at a restricted air filter. A restricted air filter will also cause less boost. Running 1 to 2 psi at cruise depending on your final drive ration tire size and rolling resistance is not out of the ordinary with the ATT. 12 to 16 boost is normal for the ATT as top boost. You are flowing much more cfm with the ATT at 12 psi than you were with the gm at the same PSI boost.

The whole concept of the ATT was not boost psi but flow CFM and cylinder efficiency with minimal back pressure. Boost psi is not the holy graile it is a combination of them both. Your truck is running closer to its design efficiency now than before, every little bit makes a difference now.
 
Buddy can you 2x check; IIRC only K1500 truck got MAF in 99, My 98 K1500 had it 98 C1500 Burb did not.

MMCA do you have a scanner to see what PCM is seeing, I suspect bad MAP (boost) sensor, I once had a bad (high) MAP on mine, with my fooler in it GL4 did not code, without it it did code, fooler was masking bad MAP giving 25psi boost levels with fooler removed. With ATT I've defueled once on a hot day high IAT as seen on the scanner in the Burb but got no P0236, just defuel & max limit of 50mm^3/1000 fuel until I reset with ko/ko
 
It did not defuel, still ran the same. The air filter is about 7 weeks old, but maybe the cheapy air filter I bought is too restrictive.

I was thinking it might be the MAP sensor also, with installing the new turbo and changing injectors 2 times in 6 weeks, maybe I damaged something?

I do not have a scanner. Is there anyway to check it with a digital multi-meter?
 
Check what? It probably doesnt have a MAF, it was just an unanswered question, there are a lot of nuances to specific years and body styles....
 
buddy said:
Check what? It probably doesnt have a MAF, it was just an unanswered question, there are a lot of nuances to specific years and body styles....
Click to expand...

Your earlier post read as a statement to me not a question when I 1st read it, so I didn't know if you were referring to some text that said 99 burb had MAF or other 1st hand experience. On re-read now I see it was posed as a question.

Guy as far as I know all Burbs were F engine equipped and also AFIK only S engines got MAF.
 
Got the code again last night.

Is there a way to check out the MAP sensor with a Digital Multimeter, ohms,voltage current??????

I do not have access to a tech manual.
 
Make sure there is 5V across pins A and C of the harness with IGN on.

At idle and IGN on you should see 1.4V on pin B, so would have to poke through the insulation of the wire with it plugged in. As boost increases this voltage increases. You could tap into it and monitor while driving. If it goes too high, over 4V it would set some codes. If it doesnt go up at all or is below 1V at idle it is probably your issue.
 
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