interface w electronic distributor for diagnostic

Forum 2005-2010 (read only) Hardware Interfacing
1

Quick background, my sister broke her car, dad fixed it to a point, but we think the distributor or ECU is bad, both expensive. So to figure out which one it is, you can check the voltage the ECU gives the distributor or check and see if the distributor is giving a spark.

So, question. How can I safely get the voltage that is being sent to the distributor, it's supposed to be 4 volts, I could use a comparator as a "yes it's 4+ volts" but I'd like to get the actual voltage without frying the ECU or turning my arduino into a molted piece of plastic since I figure their might be some serious amps going through these components.

Second question, is there even a good way to see if a spark is being sent by the distributor? Maybe something like a hall effect sensor???

Also if it helps I'm going to be powering the arduino through the cigarette lighter port with a USB adapter, then ground out to the chassis for a common ground.

2

Noted.

Part of the problem is the car only experiences this problem for 30 seconds or less, so trying to hop out of the car, pop the hood and test voltages is tricky. And the trick with the grounding the plug would work if you had a second person to turn the ignition ;).

I'll work up the circuit and post any results or burnt chips later.