Micro Squirt O2 Sensor, Picking up False Signal Options

[Mblizzard]

My O2 gauge is getting some really bad values. I have a dash mounted gauge that seems to be reading correctly but the ECU is seeing values that range from 0.4 to 22 in less than 1 second.



In fact I disconnected the O2 gauge from the ECU and it was still getting the same signal. I even installed a new O2 sensor and got the same results.


Any thoughts on solving this?

[McMark]

Your O2 controller should NOT ground through the ECU. You're correct about the MS having a dedicated sensor ground. But the O2 sensor isn't technically a 'sensor' in this context, because the MS can't talk directly to the part in the exhaust, there is another controller that acts as an intermediary. That controller has it's own power and ground wires, but these aren't sensor power or ground. It's a subtle distinction, but important.

The O2 sensor controller is also powering a small heater element in the sensor. This takes a fair bit of power, and the ECU ground shouldn't have to deal with that much power.

The O2 controller should ground to the same place as the ECU grounds (Pins 22 & 23). Usually these ground to the engine case, but yours may be elsewhere.