OK, There is this one little bug with my 84 to 91 dash swap, that is just driving me nuts. It's the SES light. I just can't get it to work the way right. On the 91 dash, the wire that goes to the SES light is brn/white off of C207. On the 84 wiring, the white/grn wire came off of c207 and then went into a 'light control module' and then to the light. So I've taken the 'light control module' out of the 84 dash, and wired it up as follows. blk=ground pink/black=12v source yellow=connected to brn/white wire that goes to light white/grn= connected to white green wire that goes to computer Doing this, the SES light comes on and stays on. So I thought maybe something was wrong with the car. So I unhooked the white/green wire, and the light stayed on??? That doesn't make sense, it should have went out I would think? Here is a link to the schematic for the 84 light module? Anyone know how the SES light is suppose to work on either a 91 or 84? Am I just doing something wrong? Thanks Chris.

Also, does anyone know what voltages I'm suppose to have at any of the wires during key first on, and when the car is running?

anyone?

I'm looking for an answer to this one as well.

I've converted to a Megasquirt, and I'd like to take advantage of the "Check Engine" light in the form its in now.

I could apply either 12V, 5V, or ground to the white/green wire whenever I'd like, but I don't know which will turn it off. I'd rather not find out the hard way.

What signal does an 84 ccc ecm('8079 ecm) apply to turn it off?? If it grounds the wire, am I gonna need any resistance? Any idea how many amps I'd need to sink/supply?

Hey there, pizza guy.
Two easy ways to make the CEL turn off:
1) pull the light bulb
2) remove the Light Driver Module - it's a box in the dash with 4 wires: pink/black, yellow, black, white/green.

Hope this helps.
Lou

I'd like to be able to turn it back on under certain conditions, not just remove it.

I can control the outputs on my ECM, and can use my ECM to signal me through the Check Engine light. Only if I know how to properly turn it off.

Sorry, I misread your post. My bad.
Try doing a search for "Light Driver Module" and see if anybody has an answer for ya.

Lou

Been there, done that, that's how I found this thread and thought somebody might have an answer by now.

I'll try posting in the DFI/ECM board, maybe I'll have better luck there.

ANSWER: The 8079 ecm grounds the signal from the LDM to turn off the "Check Engine Light"

Perfect!!
I'll bookmark this thread, I'm sure the question will come up again.

Thank you!
Lou

My ecu is 9081. I just finished wiring in an LDM and i now have a solid SES. I'm assuming this ecu grounds to turn off also. if i disconnect the ground from the ldm, no more light at all, therefore, i am failing to make the connection to the ecu grounding this sigal to turn off the light.