Possible issue with ~3 year old AEM UEGO Wideband o2
 

OK so my sensor has faithfully served me for a few years but lately it has been getting trippy. I know the normal process is free-air calibrate it, then try to replace the sensor if doesn't work. However, from what I've googled the AEM UEGO doesn't have a free air calibrate function and apparently something is built into the harness to make each sensor "even" or something of that sort. I am mostly concerned since the UEGO is wired into my Megasquirt and if its reading wrong, I believe the MS can adjust the fuel and stuff on the fly, but I know this isn't the ideal way to be driving around, especially aggressively. Here are my symptoms:

Start up the car, everything is fine.
Warmup cycle, everything is fine.
Drive for a few minutes, all good
After about 10-15 minutes the issues start as follows
1. the gauge will stick between 14:1-15:1, it will move a tenth or two here or there, but just hover in that range.
2. When I let off the pedal in gear and feel the car slowing down with the injectors off, the gauge shows the same 14-15 instead of falling to the very end with the injectors off as before
3. Going WOT does not bring the gauge to 11.5 as before, even though the car pulls just like it did prior to this, again, just hangs between 14 and 15
4. Throttle tip-in where it would usually go rich, then lean up a bit, doesn't happen, just hangs between 14 and 15 no matter what i do, again, hovering back and forth a maybe .1-.2

Shutting down the car for a few minutes and re-starting it basically re-starts the above cycle of working fine, then getting stuck in that range. Ive heard of wideband sensors reading lean all the time, or not reading at all, but this seems strange, and since I can't free air the sensor, I'm basically left only with the option of replacing stuff. So what I want to know is, does this sound like a sensor issue, a gauge issue, somehow an MS issue, or maybe something else? I believe the car is still running at the AFR that my tuner programmed into it, however with a lot of work by the ECU to correct the wrong its reading from the wideband.

Have you tried replacing the 02 sensor?

I have not. Trying to not buy parts until I'm more or less sure of the issue. Also my friend has a hookup on innovate gauges so I could get a whole new one for the cost of a sensor, but then would need to change MS settings to match what the new gauge reads

Had the same issue, sensor is ded

was yours also an AEM ? Mine is the AEM 30-5310 and it looks like the sensor I need is the 30-2001. Is it just as simple as swapping one sensor for another or will I need to go into MS and mess with voltage inputs


http://www.aemelectronics.com/products/sensors-connectors-accessories/wideband-sensors-bungs-accessories/wideband-o2-sensors/bosch-lsu-4-2-replacement-o2-sensor
seems like there's some kind of calibration resistor or something built into the harness connector

No mine was a zietronix, doesn't matter though all these controllers use an OEM sensor used on all Audi/VW/BMW vehicles. Your local parts store had them in stock most likely.
Bosch 17025 Oxygen Sensor

I have the old AEM box without the gauge and the sensors die once in a while. I've replaced one or two over the past... 13 years? Not sure exactly how long I've had it, it, think I got it in 04.

We just had one die, just make sure you buy the correct sensor, AEM changed to the LSU 4.2 in the last few years.

It was the sensor, replaced and all is good again. Thanks everyone.