GM L5P TMAP (Temperature & Manifold Absolute Pressure) sensor clogged with soot at 17,500 miles - S&B MAP spacer

wwillson

Staff member
Joined
Aug 20, 2003
Messages
6,749
Location
Colorado
I have read many threads on diesel forums about the somewhat problematic TMAP sensor on the L5P Duramax. The sensor sits in the intake and can collect enough soot from the EGR that it can malfunction and cause rough idle and drivability problem or throw a code, which could leave you sitting until you replace the sensor.

There seem to be a couple fixes. One, buy a OEM sensor and keep it and the tools needed in your truck. Two, S&B makes a TMAP sensor spacer that gets the sensor out of the manifold and out of the soot stream.

I purchased an new OEM sensor - GM/ACDelco part #12681993 to have on hand in case I ruined the sensor in the truck trying to clean it and to have a spare on hand if I successfully cleaned the sensor currently in the truck.

Our 2021 Chevy HD Duramax has 17,500 miles, mostly pulling our 20,000 pound 5th wheel. I expected the sensor wouldn't have much soot on it, because the exhaust temperature is usually elevated pulling our trailer.

Tip: The wiring harness connector is impossible to get off, until you figure out the secret. Slide the tab toward the connector, then push down on the tab, it will come right off. I won't tell you how long it took me to get it off the first time.

This is what I found when I pulled the sensor.

IMG_0642.JPG

IMG_0643.JPG

IMG_0644.JPG

IMG_0645.JPG

IMG_0646.JPG

IMG_0647.JPG

IMG_0651.JPG


This is what the new sensor looks like
IMG_0648.JPG

IMG_0649.JPG


The original sensor cleaned up with MAP sensor cleaner and look pretty much like new. There is a TSB from GM that states not to clean the TMAP sensor with MAP sensor cleaner, but I didn't listen. I was careful not to spray the cleaner directly into the port in the base of the sensor where the air pressure sensor is located.

I installed a S&B MAP spacer block and reinstalled the original cleaned TMAP sensor. I took the truck for a drive and all is normal. I didn't notice any difference in the way it sounded or drove. A tip if you install the S&B spacer. Turn the TMAP sensor as you push it into the spacer, it will go right in. If you try to push it in without turning it, you'll be frusty and won't make any progress.

My plan is to pull the sensor in about 5,000 miles to see how much soot is on the sensor.

IMG_0652.JPG
 
Last edited:
The S&B spacer works. And no there isnt a maintenance interval for that part that GM knows will eventually clog and throw a code. 2019 3500HD.
 
EGR compliant diesels are an endless soot mine within the intake manifold(s). I’ve cleaned out mounds of soot out of them on 6.7 PSDs. 6.7/8.9 Cummins is about the same too.
 
The GM 3.0L EGR system uses exhaust gas after the DPF, which pretty much solves the problem of soot in the intake. I wish GM would do the same on the 6.6L Duramax.
 
Last edited:
Update 4,000 miles after installing the S&B TMAP spacer.

This is what the TMAP sensor looks like now, I'm very happy with the results. I think I'll pull it out every oil change and clean it.


IMG_1074.JPG

IMG_1071.JPG

IMG_1070.JPG

IMG_1069.JPG

IMG_1068.JPG
 
Last edited:
Thanks so much for this tip! While I myself do not own a DMAX, my boss recently brought home a '21 Sierra 2500 with the DMAX. I sent him your advice not 5 minutes ago.
 
The S&B spacer just extends time until it gets sooted up, it will eventually get as bad as it was in the OEM position. The sensor is only like $15 I just change them every couple oil changes and keep one in the center console. That said I went 50k before I checked it the first time on my 19 and while it was nasty I had no codes, and looking at it through GDS2 it was working just fine. It's a crap design, but I think all the worry over it is overblown, especially for a $15 part that takes less than a minute to change.
 
Imagine what the intakes look like on the iT4 versions and not the FT4 (DEF) versions! FT4 uses less EGR because of the DEF. I know my MAF sensor and intake grid heater on my 2012 Cummins were a mess the last time I had the intake off...

Just my $0.02
 
a GREAT example of why FORUMS can be a worthwhile read, thanks for posting!! i like to learn on forums to possibly prevent issues for anything i own!! Diesel power is great IF really needed BUT many just put put around + show off their manly BIG $$$$!!!
 
Back
Top