Hey everyone,

I'm helping a friend who just bought an 84 that he bought as an unfinished project car. The motor is an 86 Vette L98 and the wiring harness/ecm is 88 IROC. He bought the car not running. What we discovered was that the ECM was not getting power on orange wire B1. There are some high up on the driver's side kickpanel that are hot, but they don't seem to go to the ecm. The orange wires on the passenger side that go from the ecm to underhood are the ones that are not hot but apparently need to be.

I've pored over the Chiltons's 88 F wiring diagrams, it seems that the orange wires are supposed to be always hot. However, they are not. It is not clear to me where they are supposed to hook to a hot wire. If we splice an orange wire under the hood to a wire that's always hot, then the ECM gets power and the car will start and idle. However we would like to fix it right. If anyone can share some knowledge or send me a relevant 88 wiring schematic, that would be great.

 

There's usually a 3 Amp fuse in the fuse box that's supposed to supply always hot to the ECM. You can also find wiring diagrams on AutoZone.com - Get in the Zone! (click on Repair Info, Vehicle Repair Guides, Wiring Diagrams)

HTH

 

On my '84 the hot wire for the ECM comes directly from the positive battery cable. Look for a single black wire coming off the positive cable that goes into a connector that looks similar to the O2 sensor connector.

 

The wiring diagrams from autozone are identical to the ones in his Chilton's book. Not helpful enough.

I did check the ecm fuse in the fusebox and didn't think it was the problem. I thought it was attached to the pink/black wire that went to the pcm.

 

You may be right, in some cars the only fuse for the ECM in the fusebox is the 10A gage fuse going to pink/black, but in others there's also a separate 10A fuse labelled ECM. It seems to depend on what kind of fuse box has been used. See if there's an inline 20A fuse (#2) on the right front fender. It's a regular 2 prong fuse in a water tight plastic enclosure. It should be always hot, and going to orange B1 & C16. (A search on Google is always useful

 

I did see this 20A fuse in a little box where you said. We couldn't figure out how it would get power. Do you know where the other end of that harness is supposed to end up (i.e. get power)? And there were two more along with 2 relays in a "sub-harness" that could be unplugged right near there. As near as we can figure, that sub-harness is for the AC.

Thanks for the response.

 

I seem to be at the end of my usefulness here, having never worked on these cars nor is nowhere near one. It's high time someone else chimes in here, but it's likely as 8492bird says; it's hooked up to the black positive battery cable somewhere near the fuse. You are probably right about the other 2 fuses and relays. I guess they were used for a dual cooling fan setup where one fan is controlled by the A/C.