Bedwards923

It is not a Flex Fuel truck. The dealership said there was no fuel alcohol reading on the scan tool when it was checked today.

Hi all. I have a 2018 Silverado LT with the 5.3L with 58500 km on it. The truck has had several exhaust leaks, which the dealer has rectified under warranty (passenger side manifold replaced, as well as the manifold/downpipe gaskets on both sides). An upstream O2 sensor was also replaced, as it was failed after my first dealer visit. Under light acceleration, I can still hear a very minor "tick," but the dealer has assured me they have inspected the exhaust system and found no leaks. I recently bought an OBD2 scanner, and I've noticed that my LTFT's are extremely low negative numbers. At idle, I have seen as bad as -25%, but it usually hovers around -17% to -22%. While driving, it is generally around -13%, but sometimes it's lower than that. I am getting these numbers on both banks (sometimes one bank is like 2% difference). The dealership said the throttle body air flow compensation value was at 67%, so they cleaned the throttle body and did an idle relearn. Compensation value is now 0%. I have also cleaned the MAF sensor, and tried blocking off the EVAP purge solenoid vacuum line to see if it changes the fuel trims, but they are still the same. The air filter is clean and basically brand new. I've never dealt with negative fuel trims before, and I am kind of at a loss of where to go. I've heard of these trucks having problems with the high pressure fuel pump, but I'm not sure how to really diagnose and confirm that. Any suggestions or advice would be much appreciated!