constant 12V to ECU

[tording]

Ok. I am throwing a code 15 on my ECU which is the ECU memory code. I have been told on here by you guys before that either the ECU is not getting the constant 12V on pin 1 it requires or there is something bad with the ECU itself. This wire that goes to pin 1 on the ECU and carries this 12V where does it start? What does it connect to to get the constant 12V? I want to check it and make sure that it is connected but I don't know where to look. Thanks in advance for your help.

 

[HISSIN50]

As I recall, it sources power from the solenoid (with an inline fusible link as circuit protection).

By chance, do you have a chip installed?

Good luck.

 

[tording]

I have heard that the chip can throw this code. I do not actually know if I have a chip. I have yet to unbolt the computer because it is such a PITA to get back up in there into position that I dont want to do it if I don't have to. I thought it might be easier to just see if maybe the wire was unhooked or the fusible link is bad or something. Is there anyway to find out which fusible link it is and test it to see if its bad or not?

 

[HISSIN50]

To me, the fact that the puter powers up suggests the fusible link and wiring are okay.

You could sure put a meter on the wire and note that it does not lose voltage (check it periodically). Maybe a tell: WHen you normally disconnect the battery and reconnect it, does the idle kind of hunt for a few minutes while it relearns? If so, but the car doesnt normally do this hunting day in and day out, to me that would suggest the KAM is not losing power. I'm weird and look for little clues like that.

For more/better diagnostics, I'd wait for Jrichker, Jason and the other smart puter folks.

Good luck.

 

[jrichker]

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

 

[tording]

Well mine is a 92 so I looked at the EEC pinout on that website for a 92. It says its a yellow wire that goes to pin 1 on the ECU and comes from fusible link G. Anybody know where fusible link G is located on the car and how I identify it?

 

[stang&2Birds]

First, see if you have +12v at that pin. If you have +12v, don't worry. If +12v is not there, you can wire in a new wire (with a wire fuse in line).

You need a full wiring and harness diagram. Even then, the diagrams and locations are some pure BS that someone put together to say that they had documentation. I have *3* different *FORD* wiring/harness '86 diagrams. And, not one of them was exactly what was in my '86 T-bird. Close, but not exactly the same.

Maybe by '92, Ford may have figured out how to properly document the cars they build. Hmm, NAA!

 

[tording]

In order to check that wire at the ECU I have to unbolt the ECU from the kick panel and I hate doing that. It always seems like once I get the ECU down I cant get it back up in there the same way so I didn't want to do that if I dont have to. I guess I will have to though since nobody knows where this damn fusible link is.

 

[tording]

So I just took my ECU out and guess what I found? Yep. A hypertech chip. So I guess thats why I was getting my code 15 thrown and why it detonates if I don't use 93 octane fuel. Now, what should I do? Leave the chip or take it out and run the stock computer?
Its the standard Street runner chip Part #689021 from hypertech. I don't know if I should leave it or not. If I leave it do I need to do anything with the code 15 that is being thrown? Also the chip says its for an 89. My car is a 92. It does say its for an 5.0 HO and a 5 speed which my car is. It should not matter that it is for an 89 really should it since there is no difference between and 89 and 92?