Nistune Forums

A question regarding the 02 sensor voltage (or lack thereof).

The 02 values in nistune have always read zero for me, so I did some digging to find out why.

I figured out I had the incorrect EFI loom installed on my car which is has an 86T ECU. The loom was set up for a zirconium sensor (as ecu pin 115 was wired into the yellow wire of the sensor plug, and the car was actually produced in 84).

So to convert the loom i just cut the yellow wire (pin 115) from the ECU and grounded it - and left pin 115 floating.

So now I have the titania sensor in (17mm, red white black wires), working, the heater is working (it heats up, has 12v to it), and I have put the multimeter on pin 24 of the ECU with the ignition on and I was getting around 1v - however in the Nistune app I'm still not getting an 02 sensor reading.

Is it possible I have killed the o2 sensor ADC circuit by having the incorrect wiring? What else can I look at to get this working, as I don't really want to run in open loop the whole time, etc.

Check your O2 sensor input (one showing 1V) as the engine is running. Assuming it is not running too rich then it should be hovering around the 0.2 - 0.8volt area. I dont think the O2 input sensor AD input should be damaged. Check pin 24 whist engine running

Pin 115 is power for the O2 sensor heater, but not used on RB30s and later VG30s for example and was left out

Okay, tried that, got a steady 0.960v with the engine running - however it has had the 440cc injector swap, but it's running fairly rich due to only the rough injector re-sizing applied.

I figured it would be running rich and not being able to get itself even close to 14.7, however, i figured it would at least show me a constant high or low voltage in Nistune? or is this something i should worry about when I get it tuned (I will probably take it somewhere).

Once engine is over 30 degC with o2 feedback it should start swinging. Try making it report lean instead of rich by temporarily pulling down K constant at idle to see if O2 sensor reports a lower voltage

I will have to get back to you on this, as I now have something wrong with my charging system - as the voltage warning light on the dash is staying on when the car has been shut off and flattening my battery, replaced the alternator, and it hasn't fixed it ... maybe time for an auto-elec

Sounds like your ECU is keeping power held up to the ECCS relay. It should click 'off' after 5 seconds after key

Unplug the ECU to see if this is the case and if the light turns off