I've been fighting with P0031 code in my 2006 Matrix XR for awhile now. I have replaced the upstream 02 sensor, thinking it would go away, but it hasn't. Since then I have attempted to narrow down the problem. Tonight I checked both Fuse boxes (at first EFI1 and EFI2 fuses since the wiring diagram says they affect the 02 sensor directly). I switched up the relays thinking maybe that was issue, but nope. I even went as far as climbing under the driver's side and opening up the in cabin fuse box and checked every fuse in there. I even put in new fuses into the EFI1 and EFI2 thinking maybe there was a problem with one of them...nope. The manual says it goes Battery -> EFI1 Fuse -> Relay -> EFI2 -> ECM. EFI&EFI2 might be switched around I don't have the wiring diagram with me, either way both fuses were replaced and I swapped out the relay.
The code is still there! I've reset the car with my scantool, unhooked the battery tons of times, but it always comes back.
Thinking it was a short, I peeled back the tape on the wiring that goes to the clip harness (where you plug in the 02 sensor plug) to see if there was something broken or shorting. Everything appeared to be fine. I even went as far as splicing into the 2 black wires and checking with my voltmeter to see if there was actually power going to the 02 sensor plug. I first tested the bigger of the black power wires, it was a constant 13V or there about, and then I tested the smaller black wire, it was around 3.0-3.5V constantly.
I checked the ECM to see if a plug was loose, everything was plugged in, I pushed everything down to ensure something wasn't loose.
I've been fighting with P0031 code in my 2006 Matrix XR for awhile now. I have replaced the upstream 02 sensor, thinking it would go away, but it hasn't. Since then I have attempted to narrow down the problem. Tonight I checked both Fuse boxes (at first EFI1 and EFI2 fuses since the wiring diagram says they affect the 02 sensor directly). I switched up the relays thinking maybe that was issue, but nope. I even went as far as climbing under the driver's side and opening up the in cabin fuse box and checked every fuse in there. I even put in new fuses into the EFI1 and EFI2 thinking maybe there was a problem with one of them...nope. The manual says it goes Battery -> EFI1 Fuse -> Relay -> EFI2 -> ECM. EFI&EFI2 might be switched around I don't have the wiring diagram with me, either way both fuses were replaced and I swapped out the relay.
The code is still there! I've reset the car with my scantool, unhooked the battery tons of times, but it always comes back.
Thinking it was a short, I peeled back the tape on the wiring that goes to the clip harness (where you plug in the 02 sensor plug) to see if there was something broken or shorting. Everything appeared to be fine. I even went as far as splicing into the 2 black wires and checking with my voltmeter to see if there was actually power going to the 02 sensor plug. I first tested the bigger of the black power wires, it was a constant 13V or there about, and then I tested the smaller black wire, it was around 3.0-3.5V constantly.
I checked the ECM to see if a plug was loose, everything was plugged in, I pushed everything down to ensure something wasn't loose.
So now I'm stumped as hell. Any ideas?
Did you put in a new oxygen sensor or air fuel ratio sensor? What brand did you use, hopefully you did not have to do any splicing? If you used anything but NGK or Denso, you will have a problem. What is the part number for the item you put in your car? Do you have a stock exhaust setup?
Did you put in a new oxygen sensor or air fuel ratio sensor? What brand did you use, hopefully you did not have to do any splicing? If you used anything but NGK or Denso, you will have a problem. What is the part number for the item you put in your car? Do you have a stock exhaust setup?
I used a Denso upstream A/F sensor, OEM type replacement. The connection and everything was exactly the same as the old one, and the a/f sensor looked identicle to the old one. I even asked the parts place if it was the right one for my engine type and they said yes. I don't think that's the issue. Yes on stock exhaust, car is completely stock, it's my wife's car.
Interesting that Denso sensor did not fix it, it always fixes that code. Usually what happens is people cheap out and get a bosch or a universal, then they buy the NGK or denso sensor and then it is fixed. Since you did not cheap out, it is unlikely that the new sensor and wiring is not defective and you reset the ECU, which is the correct way to do it.
Just to confirm, you replaced the sensor that is accessible from under the hood, and not the one under the car? How is your gas mileage and how many miles do you have? Looks like an ECU problem, which is actually somewhat common on the 06 corolla/matrix. PM fishexpo101, he maybe able to help you.
The Following User Says Thank You to mikered30 For This Useful Post:
Well it's only that code and honestly I'm not going to take it to the dealer, those jerkoffs wanted $340+ for the rear 02 sensor when I replaced that 6 months ago. I got it from a parts store in town for $120.
P0031 is not an Air-Fuel Ratio sensor code, rather an O2 sensor code. The heater circuits are completely different between the two as are their operation. The AFR sensor will read a constant 3.3V on the positive side and 3.0V on the negative side (not the heater wires, but the actual sensor wires). AFR sensor heaters are ECU controlled with a duty ratio cycle; O2 sensor heaters are not.
If you have an AWD Matrix, they use O2 sensors, not AFR sensors.
For clarification:
2WD 2006 1ZZ Matrixes use air-fuel ratio sensors. P/N: 89467-02020 or 89467-12010; Denso P/N: 234-9052
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