After Engine Swap Downstream O2 Sensor Question

[06YarisRS]

I think I have to replace my downstream o2 sensor as I'm getting a related code. I think there may be a short or intermittent open circuit as the wiring was twisted and isn't in great shape. The problem is that the 2011 Corolla connector and Yaris connector are different. Will a Yaris o2 sensor work? I have not been able to find any o2 sensor that lists compatibility for both vehicles.

[tmontague]

I am using my OEM yaris connector without an issue. The upstream one would have to be specific to the engine but not the downstream one. The downstream one is a "dumb" o2 sensor not like the upstream one which is a wideband sensor and controls afr's

[06YarisRS]

I am using my OEM yaris connector without an issue. The upstream one would have to be specific to the engine but not the downstream one. The downstream one is a "dumb" o2 sensor not like the upstream one which is a wideband sensor and controls afr's

Thanks Trevor. You say you're using the connector, you mean the whole Yaris o2 sensor, correct? I see Denso sells one that requires splicing. I think my problem is due to the wiring as it's very intermittent. If I can fix the wiring, I'll just use it, otherwise I'll just order one. Thankfully the downstream ones are a lot cheaper. I bought a real cheapie off ebay a while back for my '06 and had to put a defouler on it, but worked fine after that.

[tmontague]

Yes, I have the whole yaris part, sensor, wire and all.

What's the code being thrown, P0420?

[06YarisRS]

Yes, I have the whole yaris part, sensor, wire and all.

What's the code being thrown, P0420?

Actually, I'm getting P0138 and P0607 (ECU) but from my reading that's not uncommon with the failing o2 sensor messing with the ecu. I'm going to remove the sensor, check the wiring and use a multimeter to check if the sensor is good. It was like $16.00 or something off ebay. The fault is very intermittent, I haven't seen it in 7 - 8 starts and runs, but it appeared a couple of days ago, again.

[tmontague]

Iirc that was the code I had after I did the swap and failed to plug the ecu holes from pulling the 3 immobilizer pins. Drove across the border in a freak snowstorm with wet conditions and a ton of salt. The code got thrown on my way home. Plugged the holes and it never came back.

Jus t something to keep in mind if your o2 sensor checks out. Could be a faulty ecu or simply a short caused by some water

[06YarisRS]

Iirc that was the code I had after I did the swap and failed to plug the ecu holes from pulling the 3 immobilizer pins. Drove across the border in a freak snowstorm with wet conditions and a ton of salt. The code got thrown on my way home. Plugged the holes and it never came back.

Jus t something to keep in mind if your o2 sensor checks out. Could be a faulty ecu or simply a short caused by some water

Yeah, I read that in one of your posts. I'm optimistic that it's just the o2 sensor. If it did turn out to be the ECU, there's plenty of those available on eBay and they're pretty cheap. I did lose one of the tiny plugs when I swapped the pins and I put a dab of rtv in the hole sealing it off. I can't see how any moisture has gotten in as the car has been bone dry in the garage. I won't rule anything out though. It may be a bad ECU, but I ran the car many times and drove it before the code appeared.

[ArmstrongRacing]

The 138 code is due to a high signal voltage from the rear O2, it would be weird for that sensor to have an issue since it never gets touched during the swap. The connector is behind the dash and the wires pass through the fuse box back to the ECM.

The 607 is strange, could be due to water ingress or corrosion, or bad connections.

I would start by looking at freeze frame data, then disconnect the battery. Then disconnect the engine harness plugs, inspect closely, then reconnect everything.

[06YarisRS]

The 138 code is due to a high signal voltage from the rear O2, it would be weird for that sensor to have an issue since it never gets touched during the swap. The connector is behind the dash and the wires pass through the fuse box back to the ECM.

The 607 is strange, could be due to water ingress or corrosion, or bad connections.

I would start by looking at freeze frame data, then disconnect the battery. Then disconnect the engine harness plugs, inspect closely, then reconnect everything.

Thanks, Tom. Since I changed the midpipe, the sensor was unbolted and rebolted. The wires had been twisted a bit when it was replaced a while back. I had replaced it as I had had a code (if I recall P0420). I did have to use a spark plug defouler as the cheap o2 sensor - about $20.00 on eBay - didn't fix the issue. I ordered a sensor from Rock Auto yesterday and will install it. I'll perform the checks you suggest.

[atomic_hoji]

Any luck with it?

I'm in the same boat as above - swapped the stock Yaris one over without trouble. Sounds like maybe your sensor wires got mucked up or the sensor itself banged about a bit? Did you solder or repair any wires related to the O2 sensor?

-- Adam

[06YarisRS]

Any luck with it?

I'm in the same boat as above - swapped the stock Yaris one over without trouble. Sounds like maybe your sensor wires got mucked up or the sensor itself banged about a bit? Did you solder or repair any wires related to the O2 sensor?

-- Adam

Hey Adam. I haven't addressed it yet as I've been tied up with the A/C issues, which - at least for now - appear to have been resolved.

I think my new o2 sensor arrived to my US post box today, but I likely wont pick it up until after Christmas now. I'll be sure to let you know the outcome. The wires on mine were messed - twisted badly, so I'm guessing an intermittent wiring issue, maybe triggered when the exhaust shakes a certain way at startup. It's really random. I started and ran the car many times yesterday and today and no MIL, though I haven't scanned for pending codes. I can't say if there are any drivability issues as the car is back up in the air and hasn't been on the road. If after I replace the sensor the code reappears, I'll follow Tom's recommendations above. Are you getting the P0607?