- My model of MX-5 is: NB Arctic 1.8 (2005)
- I’m based near: Surrey
- I’m looking for technical help or recommendations on: Oxygen sensor troubleshooting
Hello all! I picked up a new-to-me MX5 NB a couple of weeks ago. What an awesome car - loving it so far. It’s got the CEL on and the above codes. So far I’ve managed to test two things:
-
Heater resistance: this is reading as 6.5 ohms when sticking the multimeter probes into the sensor black wire connectors. It is very interesting that I’m getting P0031 (i.e. resistance too low) but the sensor is giving me ~0.9 ohms higher than the manuals suggest?
-
Power to the sensor: I have no idea if I’ve tested this correctly, but with the ignition on (car not running), I put the multimeter into 2V (and 200mV, just as a test) and put one probe on each of the sensor pins. Nothing, except maybe 0.5mV when in 200mV mode…
So, question 1: did I test the power to the sensor correctly? Or is there a different way to do it? And question 2: does it sound like it might be a harness issue rather than a dead sensor? It was only replaced a year ago after the last owner had the cat stolen and started getting this issue.
To test the oxygen sensor output, can I leave the sensor unplugged, stick the probes into the sensor connectors and run the car until things heat up? Then give it a good rev to see if the voltage changes? That should then let me confirm that the sensor is in good condition.