I found the other day that my OBD diagnostic unit will also send the Oxygen sensor voltage values to my phone. Being curious, I watched them as I drove home (32miles flats and canyon) and noticed that the upstream sensor (sensor 1) would fluctuate between around 0.1 and 0.7V at idle, while the downstream sensor sat quite stable around 0.1V. While driving, the two would, at times, mirror each other, at others the upstream would bounce by up to 1V. Not knowing how the ECM evaluates this, I thought that I'd ask the combined wisdom-Is this normal or should I change out the upstream ox sensor?
Details on Tigger, 188k miles, original engine, super, 15% pulley, 2% overdrive crank pulley, JCW CAI.
Thanks in advance,

 

I think there the same sensor so possible swap them over and see if anything changes? Not 100% on that

 

I'm not sure about the post-cat sensor but I think the pre-cat sensor should fluctuate in roughly the range you mention.

 

IIRC, full range for the O2 sensor is 1 V. It’s normal for the upstream sensor to fluctuate during closed loop as the DME adjusts the mixture. The post-cat sensor won’t read the same because the cat absorbs/uses oxygen if it’s functioning properly.

 

your readings are normal....just enjoy the car

(our cars run a little rich most of the time anyway)

 

Cool, Thanks for the info, now to return to driving it like I stole it!