I'm currently trying to wire a 1227747 ECM in my pickup. I'm trying to get the check engine light to come on per the wiring diagram. It say to wire one side of the bulb to a switched 12 v score and the other to pin A5 at the ECM, which grounds the system inside the ECM. I've done all this and checked and double checked the whole system, and the light won't come on. Is this an indication that something inside the ECM is bad or could it be something else?

 

Have you verified the ecm is powered up with constant and switched power ?

 

Yes, both A6 (12v switched) and B1 (12v all time) are good.

 

C16 ?

 

You are correct, C16 also. Not sure I have that one hooked up. If not, would that cause the MIL not to come on. Hope it's that simple.

 

Does the bulb light if you give it power and a test ground?

 

yes

 

Something else I noticed on my 1227747 schematic is that for 5L and 5.7L engine, the 5.7 being what I have, it shows the brown/white wire at A5 with a spliced wire going to pin D on the ALDL. Not sure I under stand the meaning of this wire, but on a 1227747 schematic for the 2.8L and 4.3L it doesn't show this spliced wire. Anybody know what's up with that spliced wire, and why that might keep the check engine light from coming on?