Uncoding P codes

**TylerR04** · 02-24-2009, 11:30 PM

I need some help that hopefully will save me money.

I have a 2004 Tahoe Z71 and my check engine light will come on and turn off while I'm driving but it's not flashing. It will stay on for a period of time and then turn off. It's also hit or miss if it's on when I start the vehicle. So I had a friend run his diagnostic programmer and the p code that came up was P0101 which I looked up on the internet and it told me - Mass or Volume Air Flow Circuit Range/Performance Problem. Does anybody know what this means or how I might go about in fixing this? Thanks for any help!

**MrShorty** · 02-25-2009, 11:32 AM

Does your friend's scanner pull freeze frame data? It might be useful to see what the MAF was reading when the code was triggered.

Often one of the first things I do is to clear the code, test drive it, and then see if the same code comes back or a different one.

As you've already noted, the code description for P0101 is MAF circuit range/performance problem. With few exceptions, a trouble code by itself doesn't tell us what is broken or what to replace, it simply tells us where to start looking for problems. In this case, the problem is in the MAF circuit.

Personally, among the first things I'd do would be to take a trip to the library, find the auto repair section (often in the reference section), find the "emissions, performance, and driveability" manual for my year/make/model, and look up the diagnostic information in there for a P0101. The manual will explain what conditions trigger the code, possible causes, and a basic set of diagnostic steps for diagnosing the code. Some libraries even have subscriptions to on-line services and you can access the information from home if you get a username/password from the library. Some users here have access to that kind of information, and, if you wait long enough, they might post that information (my personal preference is to go to the library so I don't have to wait). since I dont' have that information right in front of me, I can't give you the "by the book" diagnostic tree.

A "by the seat of my pants" diagnostic tree would probably start with the freeze frame data, to see what the MAF signal was doing. Then, if your friend's scanner is able to read data in real time, look at the MAF reading with the engine off and then at idle to see if the MAF signal is responding correctly. Carefully look over the wiring between the MAF and PCM (a wiring diagram would be useful) and make sure there are no obvious breaks or bad connections.

**silveradotrailblazer** · 02-25-2009, 05:46 PM

CRC chemical makes a MAF spray cleaner. Its the only MAF cleaner Ive used and it works if used per instructions. Its not expensive and this could solve your MAF problem. Dont confuse with there throttle body cleaner.