Why when I replaced MAF sensor did my catalytic converter overheat?


Asked by Feb 02, 2015 at 09:16 PM about the 2001 Pontiac Grand Prix GT

Question type: Maintenance & Repair

My 2001 Pontiac Grand Prix 3.8L 3800 had a mass air flow sensor code so I bought a
new sensor and the catalytic converter overheated. I replaced the new sensor with the old
sensor and the problem went away. Did I get a bad sensor or did I do something wrong? I
know I installed it correctly.The plug only goes in one way.

10 Answers


are you sure there are no misfire codes?


No misfire codes. In the beginning the only code was Mass Air Flow Sensor Low Input. The problem happened right after replacing the MAF. The car had been idling up and down when first started before replacing the MAF. As soon as I put in the new MAF and drove for about 1/2 mile very slow, I live on a dirt road, the engine started to lose power and almost stopped so I turned around and went home, barely making it. When I got home I smelled the catalytic converter and looked under the car and saw it glowing. I replaced the old MAF sensor and was then able to drive to town 5 miles each way with no problem but the Service Engine Light did come back on. This all started only after replacing the old MAF with a new one.

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Getting unburned hydrocarbons in the cat somehow, leaky injector or something. Don't know why the maf would matter, unless another problem is making it read through the maf. The engine light came back on? What was that code?

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Same as before, Mass Air Flow Sensor Low Input. Car runs the same as before after replacing the old sensor for the new one.. It had to be the new sensor. Thinking maybe it was faulty and telling ECU that there was a high input instead of low.


I wonder if we aren't looking at this backwards. I am now wondering if your converter is bad and gave you the maf code in the first place. Might want to get your exhaust sniffed and see what it says.

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Might be right. I will have to have that looked at.


There is one other thing I didn't do and that was disconnect the battery terminal before I changed the MAF. Could that cause it not to recognize the new MAF? And did it damage the new MAF by not disconnecting the battery first?


Probably not, but it is always a good idea to disconnect the batt before you do any electrical. I would still get it sniffed and see what they tell ya.

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Problem solved. It turned out to be a bad MAF sensor even though it was new. It caused the PCM to think there was more air flow than there actually was and caused the injectors to pump massive amounts of fuel. I Had the exhaust checked and it was fine. Bought a new MAF sensor and am now enjoying a 5 mpg increase in fuel economy. The engine runs and shifts so much better.


Awesome! Isn't it great when you finally get it fixed. Frustrating on buying bad electrical parts isn't it? It happens a LOT. Gotta wonder where they get this crap from. I have learned to go OEM whenever possible. Well, congrats and thank you for posting your fix, not enough people do this. It might help someone else some day.

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