checking for codes using voltmeter

[hinge]

Does anyone know how to check for engine codes at the aldl port on these 3.1 cars using a voltmeter? The check engine bulb/circuit is not working. I've been told the bulb has been swapped , but still doesn't work. I put my leads across the A and B pins , I get 5v there , where do I probe to get the data that flashes the bulb? Thanks

[thumbs]

you don't thats ford mid to late 80's called eec-1V {eec 4) the 5 volt you are reading is the communication voltage. you need a scan tool if i were you i wouldn't be fooling around with things you don't know untill you get more info.