After Engine Swap Downstream O2 Sensor Question

[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]

Originally Posted by 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.

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.