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MAF/O2 codes

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topher5150

Full Member
Joined
Nov 27, 2021
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15
Location
Michigan
I just picked up an 04 a couple of weeks ago. From what I was told it was throwing a MAF error code, don't know if he replaced it or just cleaned it, but a short time later the code came back. I got the codes checked today, and it was reading MAF and O2 error codes, and there's a smell of gas when I leave the truck. Could a bad MAF sensor be causing a misreading at the O2 sensors?
 
Having a bad maf sensor could lead to the engine burning more fuel (running rich) and could be interfering with the O2 sensor, and over time, may even plug up the O2 sensor with crud. That's really not good for your catalytic converter. The two sensors combined give the engine metrics on how it should be running. Without them, or with bad info, the computer starts guessing and it can cause the engine to run rough.


Unfortunately, it sounds like there's quite a bit of "I don't know" going on with your story. Who was scanning the codes? Who touched the MAF sensor last? I'm guessing it wasn't. A mechanic, as those two codes would be super specific and they would have the scanners to see the live data to know which parts are acting up. More than likely, I'm guessing it was a "sensor out of range" code, which is super vague. The O2 code is likely rich or lean.


Also, check your air filter while you're fiddling around. Make sure it's clean. Unplug the MAF sensor, inspect the pins inside it and the wire for debris/ corrosion, and then seat it back into the sensor firmly.

MAF codes will clear by themselves after so many engine cycles. So you'll want to go for a 10 minuites drive or so after doing something


Worst case scenario, go and grab a MAF sensor on rock auto and install it yourself. It's probably the easiest part to replace yourself outside of your wiper blades. But you'd really like a proper inspection before you spend too much.
 
AC Delco is OEM, it's similar to motorcraft from ford. 'GM genuine' is often the exact same part if both are present. They use it as blanket branding for their other suppliers.

Delphi makes quality stuff in general and is a direct OEM supplier of various electronics. They're often more expensive than OEM, but in those case of your MAF are actually cheaper.

Beyond that, you have your typical multi manufacturers. Bosch and denso are name brand, and dorman/ cardone are your more budget brands.

When using rock auto, ultra power is their 'house' budget brand.

You can of course also stick with things that have hearts next to the listing. Those are parts that they sell frequently and usually point to trends in best cost for the performance/ reliability.

Go with whatever you feel is best honestly for the MAF. If you just want things working and don't mind spending the cash. Go OEM or Delphi. If you bother with the O2, absolutely stick with OEM/ premium options. They're fickle little things that third parties don't always get right and their a pita to replace.
 
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I found Delphi reman at O'Reilly for a decent price. I've had a lot of bad experiences with off brand O2 sensors.
 
bosch has good o2 sensors...
 
I forgot to mention the gas after driving. The combination of the gas smell and the codes reading rich got me searching and some of the things I came up with is fuel pressure regulator. Do think the regulator is on the fritz dumping to much fuel and giving me a rich reading
 
topher5150 said:
I forgot to mention the gas after driving. The combination of the gas smell and the codes reading rich got me searching and some of the things I came up with is fuel pressure regulator. Do think the regulator is on the fritz dumping to much fuel and giving me a rich reading
Click to expand...

Test the fuel pressure.

The fuel pressure regulator on my 2003 Avalanche is mounted on the driver's side fuel rail on the upper side of the engine and is easy to change.

I think this may have changed mid-year.

On my 2004 EXT, it is part of the fuel pump in the fuel tank.

Not so easy to change.

If the fuel pressure shows normal while running and then drops off quickly after the engine is shut down, I would suspect a leaking fuel injector and not the pressure regulator.

If there is a part that is dumping way more fuel into the cylinders, I would look at a defective fuel injector.

If one of those does not close off properly, fuel will get into a cylinder either all of the time or at least at an unmetered rate.

Maybe try a high concentration of fuel injector cleaner in a couple of fills of the fuel tank and see if that frees things up before jumping in and replacing a bunch of parts.

I'm hoping all of that extra fuel has not already wasted your O2 sensors and cats.
 
Ughhhhh this thing is being so temperamental. Now for the past two or three weeks the CEL has been on again off again for a few days at a time
 
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