For the 2nd time in a few months, I got a P0101 code, which is for MAF meter reading out of spec....low voltage?

Most say, "clean the maf", or "replace the maf", due to over oiling of the K & N air filter....which I do not have.

Both times, the MIL came on in the same spot, during a 140 mile tow of car and trailer.

First time it happened, since truck has 180K, I just went ahead and replaced MAF with new, not reman, AC DELCO maf meter, and it's been OFF ever since...this was in May. Today, it popped back on...again.

I run a Wix paper filter, which is NOT oiled, but I do run a 4" straight tube with 90 degree connection from MAF to throttle body. I also run a modified factory airbox, with bottom cutout....as I have done for roughly 5 years. HPTUNER datalog have proven that it works as a true cooler air induction setup.

It was heavily raining, so I'm not sure that had anything to do with it or not.

Truck is 2002 Z71, 5.3 engine, 180K miles, 3.73 gears, stock converter, tire height, etc...

Other mods are Ebay longtubes, no cats, Dyno max 3" single outlet exhaust. Ported throttle body, LS1 F body electric fans, and HPTUNER tuned by me.

Any ideas what is happening here?
Just a fluke?

I'm not going to easily believe it's a defective, 6 month old AC Delco MAF meter....

Definitely all ears though....

 

The bench tune I got to get my truck running and get it to the dyno came with a MAF tune that was out so big on calibration with a mis-wired MAP sensor and I would throw that code after a few miles. I wired up the MAP sensor correctly and didn't get that code again. You'd have to be pretty far out on the tune to get it to throw, but anything is possible.

I bet it got wet or temp decreased too rapidly for the pcm's liking. If it got wet then it could have been damaged.

When's the last time you put the scanner on it and logged some runs? I wonder how close your VE tables are vs MAF calibration.

 

I haven't datalogged specifically for MAF calibration in quite a while.

My AFR has always been right where (it's been for a few years) and where I want it, at idle, cruise, and wot, according to my wideband (which is hardwired in)

Just been playing with timing tables the last 6 months or so, to get a knock retard-free 87 octane tune...I do peek at STFT and LTFT readings when I datalog a timing change, and it's always been 2-3 or less on both, which is why I never have bothered.

On LS1tech, a guy brought to my attention that the 01, 00, and 99 Silverados had a much higher "Delta Airflow Error" spec, and suggested simply changing mine to match one of those to keep the light off.

 

Could be a MAF, MAP or TPS sensor issue as code sets if MAF reading does not match the calculated/predicted airflow values. Maybe IAT as well. Check these sensors and their wiring. Monitor the TP sensor signals for glitches at any particular throttle position. If it only happens when wet, could have just been a wet sensor connector.

 

Just to update...

Did a full re-tune of VE and MAF on the 13th, since I realized it has been about 5 years, LOL...It was, or seemed to be, actually running pretty good, but now runs better than it has in a while.