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.

[Mblizzard]

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.

Correct the heater portion of the O2 sensor should and is not grounded through the ECU.


The separate controller and ground in the sensor appear to be ok as indicated by the proper operation of a dash mounted digital readout that came with the O2 sensor.

As shown below, the gauge/controller has a 0-5V output that sends a voltage to the ECU which is set up to read on a linear calibration scale.


That 0-5V output is going to Pin 34. However when I disconnect that wire from the ECU it is still getting a signal. It still gets a signal when I unplug the O2 wire harness from the sensor and there is no power to the gauge/controller which would have to mean no signal on the 0-5V output.

This configuration ran for over a year for my 2056 so I know it works. Could be a wire issue but with all of the O2 related wiring disconnected from the ECU and it still gets a signal for O2 it is hard to think of another place it could be picking up that signal.