Hi Peter

Why not scope the heater circuits & evaluate what is happening in real time?

I think you have a low amps clamp with Modis. If so, then I recommend that you monitor the current flowing & also the voltage on each heater wire. If you start at key off & then key on, then start up. with 60 seconds on screen, you will see enough info to establish what is happening.

Here is a post I made a couple of years ago. although now I use an amps clamp to give further evidence, as to what is going on...........

Old post....

As with most electrical systems on a motor car, it is possible or even preferable to test with a scope.

It was whilst chatting to Dave Harney about O2 sensor heater circuits, that he mentioned his method of testing. I have tried it a few times & I must admit that it has been proved to be pretty conclusive for me.

It’s a simple test taking a few moments to set up, which involves the probing of both heater wires of the Lambda sensor. In my example I have also probed the signal wire so that I can assess the time taken for the sensor to become responsive.



I hope the animation does justice to the simplicity of the test.

Cheers all