O2 Sensor Rubbing

Just wanted to share an issue I just tracked down. Maybe help someone with similar symptoms in the future.

My O2 sensor, Bank 1, Sensor 2 (Drivers side, downstream) died on me about 6 months ago so it got replaced with a new Denso sensor.

Everything was fine for a few months until the check engine light came on with a reading of "Low or No voltage at Bank 1 Sensor 2. Looked under the truck and quickly found the issue. The heat shield had rubbed its way through the insulation on the O2 sensor cable and grounded out the wire that reports the resistance in the sensor. Grounded = zero resistance! I put some electrical tape on it to protect it and went on my way. It worked fine for months.

Last weekend after a 200 mile drive the truck entered limp mode from seemingly nowhere. I got codes showing O2 Sensors Bank 1 Sensor 2 and Bank 2 Sensor 2, Mass Air Flow Circuit, and both secondary air pump injection drivers had faults. Long story short the single fuse that feeds power to these 5 systems had tripped, replacing the fuse fixed the issue.

When I got back home and done with my weekend I examined the O2 sensor again, sure enough, it had rubbed through again, and this time it seems the 12V signal got grounded to the heatshield, tripping the breaker, and forcing me into limp mode.

I removed the O2 sensor again and repaired the worn insulation, added some plastic wiring loom, and cut out the offending head shield in that area. It seems that the way the replacement O2 sensor is designed is longer than the original in that location (or I got the wrong part somehow).

Hopefully this can save someone a headache down the road or serve as a reminder to assess wiring for potential rubbing situations.

 

That entire side of that heat shield is bent. It should look like the other side.

 

It looked alright to me, it couldn't really get more out of the way because the frame was right behind it. I think the 'stem' on the O2 sensor I got was just longer than the factory one. I may have gotten the one for the passage side. I remember reading that the wire length was the only difference between bank 1 and bank 2.

...On to research heat shields now...