Hi there , Looking for any information that may lead to success with repair.
Currently troubleshooting my brothers 2003 Sierra 4.8 4 Speed Auto 2 Wheel Drive.
He purchased the truck with 130,000 Kilometres recently and the truck was Babied it’s whole life.
The truck came with a K/N cold air intake, which I believe led to the notorious P0101 MAF sensor Performance Trouble Code. At first I thought nothing of it but now it seems to have caused the truck to Have a really hard time finding its gears in the transmission , cold or warm temperatures.
I started by cleaning the MAF with the aerosol cleaner, reinstalling and that seemed to leave me high and dry .
I next found a donor truck and used the good MAF and installed. Right away the trouble code had gone away , but even after leaving the battery disconnected overnight (in hopes of resetting the vehicles computer) , it still will not shift correctly .

It is my understanding that The MAF signal for intake is used to calculate torque output from the engine in order to shift the transmission efficiently , And that if this signal is lost the trans will go into a “Limp” mode for lack of a better term. What can I do to reset this issue , or what can I do to bring this truck back to running/driving stock again?!?
First thing I will be doing is throwing that k/n filter right in the trash.

 

Is the speedometer reading? The MAF sensor will not cause the problems you are posting. If the speed sensor is bad, that will cause high rpm's, and shifting high into engine speeds.

 

Yes the speedometer is functioning.

 

good maf diagnostics so far. You did everything correct.

If I have it correct:
the maf is used for fuel metering corrections.

for proper shifting, the trans must have vehicle speed and engine load information.

engine load calculations use rpm, map and throttle position sensor inputs

 

Thanks , what can I do to correct the transmission issues . ? Scan tool relearn ??

 

Do you know if it uses a vacuum modulator valve?

 

I do not know if this truck uses a modulator on the trans , I will look into it thanks

 

Sometimes what happens is people will upgrade to a KN filter, and alter the air intake manifold without consideration to the MAF. The factory MAF is mechanically suited to the air flow of the air manifold. In other words it is sized to the air duct. If the air duct diameter is larger the MAF signal will not correspond to the air flow, then you have more air to fuel mixture.

 

What I have also heard is reusable oiled aftermarket filters can contaminate the MAF with the oil/spray used to clean these k/n filters

 

Yea, and you can clean the maf with approved cleaner. The OP says he replaced the maf with a used one, solved the issue, which also makes me think the KN filter assymbly is fine, and I'd keep it if it were my vehicle