Mystery Cel Problem! - Corolland: the Toyota Corolla Forums

Guest RollaOwner

Hello,

I’ve had some problems with my CEL on my ’01 Corolla LE with 105K miles. I recently purchased the car, so my ownership history is quite short. About 2 months ago, the CEL was on with p0171 code, so I replaced the MAF sensor (OEM). Reset ECU, and all was well. Symptoms went away and light stayed off.

200 miles later, the light comes on again with five codes:

P0171

P0100

P0110

P0441

P0446

Now, coincidently, I filled up the gas tank (not topped off) and drove on the highway when the light came on. The gas cap was securely capped, so I don’t know if this has anything to do with the EVAP codes.

I have no clue why the MAF code is being thrown. When I replaced the sensor, I had the ignition at ON or ACC to have a light plugged in the lighter outlet to see what I was doing. Not sure if that has anything to do with it or if it messed anything up. After I installed the new MAF, the p0100 and p0110 code was being thrown, along with the p0171, but then cleared the ECU, and light didn’t come back on until now with the five codes. Why all those codes at once?

I have had new parts put on recently: new spark plugs (OEM), new coolant temperature sensor (OEM), and fuel pump/strainer/filter (aftermarket). I have also done fuel injection cleaning via the stuff you pour in the tank.

Any input is appreciated!

sounds like 2 separate problems that were stored until now. I bet you got a bad sensor.

did you buy aftermarket junk?

I would have cleaned your old sensor first before I replaced it. clean it and put it back in along with some good fuel system cleaner.

this time disconnect the battery when doing the work. you will also need to clear the codes.

your evap codes could be a bunch of things and running lean po171 is probably part of the faulty maf sensor.

I do not have the test procedure for it.

very tough to diagnose multiple codes especially long distance.

Although I have an older Corolla (95), I had a smiliar experience. After I did a complete tune up (plugs, wires, cap, rotor, etc - with all aftermarket crap) I started getting all sorts of funky codes. One by one i replaced everything with OEM Toyota parts (except the rotor) and I was still getting codes. I then replaced the rotor with OEM, and all was good.

These cars do not like aftermarket ignition parts - make sure you are running OEM.

Just my $0.02 default_wink

Guest RollaOwner

Hello,

Thanks for the suggestions.

So, I decided to clear out the code and see what happens. It’s just weird the other three codes would accompany the emission codes. Possibly a glitch after filling up the tank. So far I have driven ~20 miles stop and go, and a code hasn’t been thrown. Fingers crossed it stays that way..

Thanks again.