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ATT and PO236

Big T

Big T

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Location
Fullerton, CA
New to me '99 Suburban purchased in Illinois Saturday and driven to California arriving Sunday. Made the trip in 28 hours tag team driving with my son. The best scenery (Rockies) were done at night, everthing up to that point looks the same.:rolleyes5:

After filling up in Salina, Utah, was going up a a grade on I 70 and the SES light came on. Everything was running fine, so we continued on. Just checked it with a code reader and got P0236 - Turbo Boost. Truck has Turbo Boost, EGT and Tranny Temp gauges in a pillar pod just like my '95. Was not watching the boost gauge when the light came on, but it was in OD and it would never get above 6 psi in OD. It felt like the engine was lugging somewhat, but I was going 70 mph up the grade to a 7000' pass. The highest I saw the boost go on the trip was 12 psi and that was when I mashed the pedal to see what it had. The ATT turbo seems to perform like the stock GM 4/8 until you really get into the pedal. I can see why they call it a towing turbo.

Anyway, got any ideas what caused the P0236 code? After a cold start the SES did not come back on, but the code is in memory. It has the Heath GL4 flash on it. Aside from this issue, the truck ran great, though it is much more noisier in the cab than my '95. It's diesel clatter noise, not turbo whistle. Could that be the result of the ATT and the punched out soot trap in the 4" exhaust vs the exhaust back pressure of the stock GM 4 and in place soot trap on my '95? Outside the engines sound very much the same.

Question for the mods: Need help on updating my sig line.
 
ak diesel driver said:
It might have been a IAT issue. Also if the TDCO has been upped to -1.94 it will be more rattly.
Click to expand...

Ambient temp had to be in the 20s.

I moved the TDCO on the '95 to -1.94 and it sounds the same outside, but it's way more quiet inside. On the '99 I can hear the clatter at 70 mph, not so on the '95.
 
The ATT is loud, plain and simple, it causes louder exhaust rumble and resonance and clatter sound. Have to get a good chambered or baffled muffler to eliminate that. Im getting a 4" tip muffler to see if it reduced the noise a bit and will let you know if that works. Easy install onto the exhaust tip.

The code is caused because of too low boost compared to Heaths programmed desired amount. Heath's PCM probably looking for 12psi in that situation with a GMX and ATT was only delivering 6, and PCM flash only allows 5.8psi difference. Im surprised he didnt just disable that code all together.
 
To edit your sig just click user cp at the top of the page, on the left side of the page that comes up is a settings and options, click edit sig.
 
buddy said:
The ATT is loud, plain and simple, it causes louder exhaust rumble and resonance and clatter sound. Have to get a good chambered or baffled muffler to eliminate that. Im getting a 4" tip muffler to see if it reduced the noise a bit and will let you know if that works. Easy install onto the exhaust tip.

The code is caused because of too low boost compared to Heaths programmed desired amount. Heath's PCM probably looking for 12psi in that situation with a GMX and ATT was only delivering 6, and PCM flash only allows 5.8psi difference. Im surprised he didnt just disable that code all together.
Click to expand...


I think you nailed it. Had it dropped into 3rd, boost would have surged. It was but a mashing of the pedal away, but it was way dark AM and we had been on the road way too long, so nothing aggressive at that point.

Drove it about 120 miles today in heavy rain. Hopefully it cleared that nasty midwest road salt from the under carriage. Cleared the code before I left and it did not return. I like the truck and the ATT/GL4 provides some oomph when you need it. Kinda like secondary jets in a big 4 barrel carb.
 
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Big T,
Any thoughts on what you're going to do with the '99 in regards to the upcoming CA smog issues? I've got an ATT sitting in the garage but am hesitant to put it on my '99 because of this.

Lance
 
Commifornia Smog Laws

5akman said:
Big T,
Any thoughts on what you're going to do with the '99 in regards to the upcoming CA smog issues? I've got an ATT sitting in the garage but am hesitant to put it on my '99 because of this.

Lance
Click to expand...

California is looking for the simple stuff on the diesels. If it came equipped with a turbo and as long as it looks like it is somewhat factory installed then you will be good. EGR delete will get you nailed so all "s" code engines better have the EGR and better have a Kitty( or a gutted one) on your exhaust. So basiacally all smog related stuff has to be on and visible not neccesarily working 100%. The Final step is the snap test. They are looking for gross particulate exhausters, so if your truck belches out a bunch of black smoke when the throttle is matted to the floor and released, you will probably fail.
Also clear your computers of all codes before the smog test. Any code that shows up will fai lthe test ( ya its BS) but thats this lovely state.
You should see all the hopped up D-max'rs scrambling to get a kittycat and Tech2's to erase all history in the ECM.
 
dhjunkie said:
California is looking for the simple stuff on the diesels. If it came equipped with a turbo and as long as it looks like it is somewhat factory installed then you will be good. EGR delete will get you nailed so all "s" code engines better have the EGR and better have a Kitty( or a gutted one) on your exhaust. So basiacally all smog related stuff has to be on and visible not neccesarily working 100%. The Final step is the snap test. They are looking for gross particulate exhausters, so if your truck belches out a bunch of black smoke when the throttle is matted to the floor and released, you will probably fail.
Also clear your computers of all codes before the smog test. Any code that shows up will fai lthe test ( ya its BS) but thats this lovely state.
You should see all the hopped up D-max'rs scrambling to get a kittycat and Tech2's to erase all history in the ECM.
Click to expand...

Thanks for this response, as I was busy in an all hands quarterly meeting today.

I did consider this inspection matter before the purchase. Had my son check with the local smog check guy who does all the work on their work lab trucks. He confirmed it was a visual inspection and the description is in concert with yours.

The soot trap has been gutted on this truck, but it's in place. The worst case scenario on this portion is that I swap the soot trap from my '95 to the '99. As for the turbo, the plan would be to use the GM4 and vac pump from the '95 on the '99 to pass that test. Not sure if the GL4 flash on the '99 would work with the vacuum operated wastegated GM4? Help me out, where is the EGR on this engine?

I hope it does not get to that point. I watched the truck throughout the trip and it does not belch smoke.

Man I effin love this ride:D
 
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Big T said:
Thanks for this response, as I was busy in an all hands quarterly meeting today.

I did consider this inspection matter before the purchase. Had my son check with the local smog check guy who does all the work on their work lab trucks. He confirmed it was a visual inspection and the description is in concert with yours.

The soot trap has been gutted on this truck, but it's in place. The worst case scenario on this portion is that I swap the soot trap from my '95 to the '99. As for the turbo, the plan would be to use the GM4 and vac pump from the '95 on the '99 to pass that test. Not sure if the GL4 flash on the '99 would work with the vacuum operated wastegated GM4? Help me out, where is the EGR on this engine?

I hope it does not get to that point. I watched the truck throughout the trip and it does not belch smoke.

Man I effin this ride:D
Click to expand...

Is it a VIN F? If so you won't have an egr.
 
Interesting, I thought my motor was getting louder and more clattery sounding, figured it's from winter blend and ULSD. But maybe it's from the ATT.
Isn't Heath working on a GL-4 for the ATT?
 
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