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2000 Pathfinder MAF sensor/check engine light

Clunker 2000 Pathfinder bought a month ago at 150k. Engine light was on and needed work to pass emissions. Shop replaced knock sensor which cleared fault codes for oxygen sensors as well. Right after, engine light came on again, they checked it was a MAF sensor. Knowing this truck has had a head gasket replacement and has exhaust manifold leaks, would it still be prudent to look to cleaning the MAF sensor and/or replacing it first? Or is it more likely that the exhaust leaks (or possibly intake leaks) are causing the CEL to trip?

MAF’s are pretty expensive, or so I’m told. A can of cleaner is about $6.

Replacing the knock sensor did not clear the O2 sensor codes. When you clear codes, you clear them all.

You need to post the codes here, not someone’s interpretation of them. Unless you are in California, AutoZone will read the codes for free. They will give you a printout for each code. At the top will be the code, it will look something like this P0302, then underneath it will give you possible causes for the code.

Post the code number(s) here and someone here may have had a personal experience with this code on the same type of vehicle and give you some insight.

"Replacing the knock sensor did not clear the O2 sensor codes. When you clear codes, you clear them all. "

You misunderstand. I drove 1 mile from the shop with codes all cleared (they had done the repair and cleared the codes) but because I just had it in the shop I wanted the check engine light to not be on. They cleared it again, but it came on right after. They checked the code, MAF sensor. I plan to try cleaning it, but with exhaust header leaks, curious if what the computer sees leaving the exhaust being different causes the check engine code. I will attempt to get the code read again, but I will try first to use the MAF cleaner.

I see the price for a new MAF sensor is about $60-150 for the part. But I don’t want to bother replacing it if the reason for the fault is a faulty exhaust gasket instead.

Exhaust leaks can set codes, but not MAF sensor codes.

There are lots and lots of codes. There are several codes that will reference MAF sensor signals. There are yet other codes that might have nothing to do with the MAF but that a lot of mechanics will say “could be the MAF…” DO NOT just go buy a MAF sensor until you know it is bad.

So go to a chain-type auto parts store, ask them to read the current codes, write down the exact codes (format “P1234”), as keith noted, and post them.

And as long as you don’t damage it, cleaning the MAF with a MAF sensor cleaner is quite easy, won’t hurt anything, and may help some things.