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killerbee
July 10th, 2009, 10:28 AM
IIRC, there is a temp sensor post IC, near the map sensor?

Anyone know what I am talking about? I don't see any pid for it.

bballer182
July 11th, 2009, 05:09 AM
uh don't think so... just at the MAF

killerbee
July 11th, 2009, 05:19 AM
IIRC, the sensor is locate on top of the plenum, just to the left of the turbo compressor.

bballer182
July 11th, 2009, 05:32 AM
found the pid. It's a TCM pid only. "IAT2"

EFI doest say where it's located though.


Guess you could log it and make an assumption.

killerbee
July 11th, 2009, 06:23 AM
Have you seen any IAT2 dependent tables?

bballer182
July 12th, 2009, 11:27 AM
Nope. I'm gunna go log it really quick.

bballer182
July 12th, 2009, 02:23 PM
So that PID caused me about 2 hours of grief. Really long story and it makes me mad to even think about it.

So the pid i think is incorrect once i finally got it to work it read a constant -32*C no matter what i did. boost, no boost. I don't know... gotta report this to the beta section.

JoshH
July 13th, 2009, 03:13 PM
The PID for the temp sensor in the cross bridge is SAE.IAT

killerbee
July 14th, 2009, 12:12 AM
Guess I am confused now. Are you saying AAT is measured at the MAF sensor? Based on my logs, I am compelled to believe AAT is taken outside, probably the grill. It is always very close to ambient. SAE.IAT appears to behave exactly like an airbox temp on a relatively dampened CAI.

(thanks for the response!)

bballer182
July 14th, 2009, 12:20 AM
Guess I am confused now. Are you saying AAT is measured at the MAF sensor? Based on my logs, I am compelled to believe AAT is taken outside, probably the grill. It is always very close to ambient. SAE.IAT appears to behave exactly like an airbox temp on a relatively dampened CAI.

(thanks for the response!)

AAT is measured at the grill. and the IAT pid is measured at the MAF.

So Josh... this SAE.IAT what is it called in BBL?

JoshH
July 14th, 2009, 01:49 AM
I believe it is also called that in BBL. If you want to verify it is the correct one, unplug your temp sensor where it goes over your turbo mouthpiece. IIRC, it should read -40 F when unplugged.

bballer182
July 14th, 2009, 11:37 AM
Well SAE.IAT is the one that is measured at the MAF (pre-turbo) Dunno whats going on with this IAT2

JoshH
July 16th, 2009, 09:23 AM
Well SAE.IAT is the one that is measured at the MAF (pre-turbo) Dunno whats going on with this IAT2
Hmmm, I guess I was remembering wrong.

bballer182
July 16th, 2009, 10:53 AM
I'm also having trouble with the VSS from the TCM also. It reads zero all the time. Does anyone else's work?

MMLMM
July 19th, 2009, 03:10 PM
FWIW..

IAT is with the MAP sensor pre turbo on the LMMs.

IAT2 is in the Y bridge on the LMMs. IAT2 is a seprate sensor (looks like a EGT Sensor)

I can only assume LBZ is the same.

bballer182
July 20th, 2009, 12:17 AM
FWIW..

IAT is with the MAP sensor pre turbo on the LMMs.

IAT2 is in the Y bridge on the LMMs. IAT2 is a seprate sensor (looks like a EGT Sensor)

I can only assume LBZ is the same.

I'm beginning to wonder if this is an LMM thing and not an LBZ...

killerbee
July 20th, 2009, 05:04 AM
It does continue to confuse. IAT appears to be dampened on the LBZ I am testing. It suggests it is not being measure at the MAF.

Is there confirmed temp signal at the MAF (06-on)?

Cougar281
April 25th, 2010, 10:39 AM
To resurrect an old thread.... The Tech2 shows an IAT1 and IAT2 under "Engine Data 1". IAT 1 is cooler than IAT2. I've confirmed this on a running LBZ. So they ARE both there in teh data stream from the ECM. Any thoughts Ross?

killerbee
April 25th, 2010, 11:01 AM
can you throw up a log, with both shown, a 30 second high load log (use brakes) with AAT, IAT, and IAT2. IIRC, IAT is going to be a dampened slow rise (CAC heat soak) suggesting location post CAC.

If my hunch is correct, IAT is going to be pre-egr, IAT2 will be post egr.

MMLMM
April 25th, 2010, 11:02 AM
IAT2 will be quite a bit hotter under pressure (boost pressure).

IAT1 will be hotter than ambient as its read right next to engine.

IAT1 is ambient + what ever under hood temp is changing it to.

IAT1&2 should be about the same crusing with little or no boost.

Cougar281
April 25th, 2010, 11:08 AM
can you throw up a log, with both shown, a 30 second high load log (use brakes) with AAT, IAT, and IAT2. IIRC, IAT is going to be a dampened slow rise (CAC heat soak) suggesting location post CAC.

If my hunch is correct, IAT is going to be pre-egr, IAT2 will be post egr.

I can't at the moment as I don't have a working LBZ yet... Once it's in and working, I'll get a snapshot with the tech2 if nothing else has happened here.

JoshH
April 25th, 2010, 03:34 PM
can you throw up a log, with both shown, a 30 second high load log (use brakes) with AAT, IAT, and IAT2. IIRC, IAT is going to be a dampened slow rise (CAC heat soak) suggesting location post CAC.

If my hunch is correct, IAT is going to be pre-egr, IAT2 will be post egr.
There is only one IAT sensor that reads after the turbo. It is in the y-bridge after the EGR.

bballer182
April 27th, 2010, 12:18 AM
There is only one IAT sensor that reads after the turbo. It is in the y-bridge after the EGR.

there is only one that EFI currently reads, or there is only one on the truck?

JoshH
April 27th, 2010, 12:29 PM
there is only one that EFI currently reads, or there is only one on the truck?
There is one that is built into the MAF sensor, and there is another that is mounted in the cross bridge between the intake manifold runners.

bballer182
April 27th, 2010, 12:55 PM
There is one that is built into the MAF sensor, and there is another that is mounted in the cross bridge between the intake manifold runners.

k thats what i thought.

JoshH
July 28th, 2010, 03:34 PM
Just to re-resurrect an old thread. I have been looking at IAT temps, and notice the IAT PID had some strange characteristics such as an increase in temps under boost. There is no reason the temp should go up just because of boost if it is being measured pre-turbo. I went out to the truck and fired up the BBL. I scrolled down to IAT and checked what it was (just for the record, it was 135 F after it had been sitting for 1.5 hours). I unplugged the MAF sensor, but the temp did not change. I plugged the MAF sensor back in and unplugged the IAT sensor in the bridge, and the temp displayed no the FlashScan was -40 F. This pretty much verifies what I thought originally. I tried to check the IAT2 PID, but it caused an error code that prevented the data from being displayed.

JoshH
July 28th, 2010, 04:02 PM
Another update. So I put the AAT PID into my BBL file. I hooked it up to the truck and turned it on. I checked what the FlashScan said the AAT was; it said it was 91 F (actual outside temp was 76 F). I unplugged the MAF sensor and the temp drops to 73 F. Plug it back in and it goes right back up to 91 F. I unplugged it again and unplug the two temp sensors that are mounted right behind the grille, but neither one makes it change. Not sure where the 73 is coming from, but it seems maybe the temp comes from the MAF sensor unless it loses the reading from it, and then it takes it from another sensor? Is that even possible?

killerbee
July 29th, 2010, 02:21 AM
Thanks for the verifications. My guess is that 73 represents a default failure value.

This is what I have concluded as LMM facts, using logs, since this thread was started.

1. AAT is measured at the MAF, pre-turbo
2. IAT is measured post CAC, pre-EGR
3. IAT2 is measured post CAC, post-EGR
4. No sensors on the grill are PID observable (that I have seen)
5. PID Misnomers have made this topic confusing. :)

What is interesting now, is looking at some of the IAT dependencies in the peripheral, non-performance sections.

bballer182
July 30th, 2010, 12:50 PM
You have 2 temp sensors behind your grille? I only have one. The only one that i know of is just a little on the driver side mounted on a lateral support in front of the trans cooler. Where is your second one?

JoshH
July 31st, 2010, 11:37 AM
One is on the support rod right behind the grille in front of the A/C condenser. That is the one the thermometer in the mirror uses. The other one is mounted to the headlight/turn signal mounting bracket down below the turn signal on the passenger's side. I'm not really sure what it is used for.

bballer182
August 1st, 2010, 05:15 PM
I'll have to check that out.