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Fuel Mileage 2022 L5P

1.7K views 4 replies 5 participants last post by  22DMaxJD  
#1 ·
I have a 2022 Duramax L5P with 34000 miles. I recently took it in for a transmission recall and ever since, the truck has had a lower fuel mileage by gauge only. Usually when I let off the accelerator, it works its way up to 99 MPG, now it only goes up to right around 70 MPG. Also have a burning smell that reminds me of a regen when I stop and get out of the truck. Also another question. When I start the truck up it automatically goes into high idle situation!
 
#2 ·
If you haven't checked/cleaned your TMAP sensor recently I'd start there. You're truck also sounds like it is in regen, and after an updated will take a few 50 or more miles to finish learning your driving habits. If you have the time I'd go run it on the highway for 20-30 min and see if it completes its regen cycle and your MPG's come back.
 
#3 ·
.... When I start the truck up it automatically goes into high idle situation!
Is it going into elevated idle even when it's a warm start? Is elevated idle turned on in the climate control menu? If it's doing elevated idle on a warm start, the ECM thinks it's cold out, possibly a failing temp sensor. An ECM that thinks it's cold, when it isn't, will not be providing proper warm engine settings (timing, air control etc)
 
#5 ·
Dealer said no recalls on my 2022, it was just at the dealer for a radio software update.