Backprobing Sensors

[jules]

does anyone know the correct technique for doing this?

i got a fancy automotive multimeter a while ago. now i know how to use the multimeter but where do you hook it up?

1. you can unplug the sensor and measure it. this sometimes works but i think it causes problems when the ECM was supplying a bias voltage, and when this interferes with the operation of the engine, interfering with the reading.
2. you can strip a bit of where the wire leads into the ECM. i have the factory wiring diagram so i can do this. this seems to be the best way, but i don't like cutting around down there very much.

anyone know the correct way?

 

[vs_berlina]

Hi Jules,

The way i've read (Gregory's workshop manual & general chatter on the net) is to remove the back of the ECU harness connector, and use a paperclip or similarly slim thing to get a reading off the back of the connector.

I've tried it on my VS, and it is quite easy to do, with just using the chassis as an earth. This way it will also show you what the sensor is reading right at the ECU itself, so if you have any cable faults etc, it will be shown here.

I would avoid stripping wire as much as possible. The chances for the patching job to become exposed later could provide you with more headaches than you originally started with!

Hope that helps!

 

[jules]

can i get this straight? where the harness plugs into the ECU behind the LH kick panel, you unplug it? won't the car stop running when you do that, now that it isn't receiving vital signals?

i'll give it a go, but to clarify, you're saying unplug the harness and probe it?

thanks for your help