So I'm in the process of switching the OH console in my 98 blazer from temp and compass to one with the fuel consumption info. The new one is from a 98 as well so there should be no compatibility issues. here's the problem; when I hook up the yellow (9th pin) wire to the purple wire in the obdII connector under the driver side dash, a yellow SECURITY light comes on in the middle of the gauge cluster and the car will start up and die immediately. So I guess I should hook the data wire to something else but I've read about 20 of these installs and everybody hooks to the purple wire. Any ideas?

 

dont know if this will help.

https://blazerforum.com/forum/lighting-electrical-52/overhead-console-temp-dir-trip-41368/

how i went about it.

 

I read your write up already, probably the best one out there by the way. I have my yellow data wire connected to the purple wire you show in the corresponding picture but it's just not working. After some more searching I did find someone who hooked there's to a wire going into the BCM. I'll try that when I get home from work. The car does have an aftermarket alarm so I wonder if they screwed up the OBDII connector when they installed it.

 

So now it's way worse. My fuel gauge is completely pinned way past full, the low fuel light is on and the security light is on. All because I hooked the yellow wire from the trip computer to the purple wire in the obdII connector. And now it's disconnected. Any ideas? I'm about to burn this thing to the ground and then kick it.

 

Figured it out, pinched the data wire I ran up to the console when I put the a-pillar molding back on. So every time I hooked it up it was grounding out the data link....Ridiculous!