First off I have an 85 IROC TPI with ecm 1226870. I recently re-located my battery to the trunk, ran power up to a distrubution block and wired a relay to the ignition to ground the dist. block when the key is on to display the LED volt meter incorporated into the dist. block. That was a mouthfull.. Anyway, prior to wiring a relay to the ignition I was probing plug harnesses, particulary the fan relay next to where my battery used to be, in hopes of finding a circut that grounds when the ignition is on. If I sent 12v to the ecm through the green wire with white stripe on the fan relay what would I have fried and how do I check this. MY single electric fan no longer comes on when temp. get over 220 or whatever it is. The fan will come on when I ground out the green wire/white stripe at the relay or at the ecm pin where ith green/white wire is. I have changed the cts and gauge temp. sensor with new ones being there very cheap. How does the ecm ground out the fan relay from the cts input and how can I test the ecm.. I opened up the ecm and found no obvious fried circuts. Any help please before I search for a new ecm. By the way I have no ses codes showing and everything else seems normal, running good.

 

This happened to my friend and I helped him by grounding the same wire. He's sending unit in the pass. side head between 6-8 cylinders was fried. I personally think thats whats going on here. I am not sure about the relay. I think in order for the green/white wire to work the relay has to be good. However I could be wrong. I know my friend changed both the relay and the sensor in the head.
Try the sensor first, or just rig up a switch so you can turn on your fan whenever you want to. That what am doing and have been doing for a year and a half now!

 

Both the temp. gauge sensor in the head and the coolant temp. sensor in the front of the manifold and the fan relay are new. I need to some how test if the ecm is working properly from the data it gets from the cts in the manifold. Besides that everything worked fine before I starting probing with 12v. places I should not have.

 

Well, if its still not turning on at the right temp. I am thinking somethings is either blown or dissconected. Did you put these sensors after you messed up or before. If before there is a chance that you have blown them.

To check the ECM ( I just learned this) just put it in diagnostics mode and if everything shows up ok your ECM is probably OK. You can also leave the two pins in your ALDL and turn the car on. If the light is flashing than its most likely working fine.
I found this out the hard way..

I am still thinking its a wire problem, or a blown sender! I am sure you did this, but check to see if everything is on right!?!?
fuses!?!?

 

I have checked all fuses and the fan relay. The fan relay and cts and gauge sending sensor are all new. I will test the ecm in diag. mode when I get home today. Thanks for the help

 

I'm in a similiar situation myself. Difference is I was wiring into the wrong green/white wire, happened to be the fuel pump relay one, by misstake.

Now I got Code 54 (which I bypass with a hotwire or the fuel pump wouldn't start at all) and also a Code 42, completely rough running engine. Hard to run without pressing down on the throttle.

 

well guys, I put the ecm in diagnostic mode by gnding A and B terminals at the OBD. This kicked the fan and all electrical sensors on. Ever since the fan kicks in by itself at about 240 degrees. Oh well, something reset I believe. Thanks for the help.

 

240 is a little high, don't you think so.
220 was factory setting!

Maybe you should still rig up a switch and control it yourself.