I posted this over in the Electronics section but not get any responses.

As most of you know I'm putting that 91 dash in the 84.
I'm trying to figure out how the service engine soon light.

Anyone with an 84, when you turn the key to on (but not starting it) does the Check engine light come on?

I always thought it did, but it's not doing it with the new dash.

If it does, I was wondering if someone could do some voltage readings for me? On C-207 (passenger side) there is a green/wht wire. When you turn the key on, do you get 12V there? When you start the car still get 12V and then it turns off?

Or before turning the key on, what is the resistance from wht/grn to ground? Short or open?

I would really like to get this last little thing working, but it's driving me nuts!

What's really driving me nuts is, from the 91 cluster. The SES light goes to a brn/wht wire that goes down to c207 which would connect to the wht/grn.

Well I'm already getting 12v on the brn/wht wire to start with. Is this normal?

I guess if anyone has a 91 and wants to test the reading of that wire for me, that will help too! All the diagrams I find, don't list voltages on any of the wires, so not sure what I should have.

Hope someone can help

Thanks
Chris.

 

well found a diagram for the 91, and it looks like the brn/wht is always 12v. When the ECM detects a problem it ground the wire, to complete the circuit and that lights the bulb.

So now need to figure out how the 84 works.

Anyone??

 

i have an 84 i will check it out later and get back at u alright

 

i checked and yes the light "check engine" does come on

but only for a while then it turns off after like maybe 5 to 10 sec

 

thanks, that's what I thought.

Not sure why it's not working.
I need to find a schematic on how it works for an 84, like I did with the 91.

I think they designed it differently between the years.

Thanks for checking.