The below images show the grounds G100, G102 & 104.











/

 

2 out of 3 were good, I fixed the other (firewall) no change.

 

I would test to see if power is making to the TECA from the relay now.

This is for 9th gen trucks.I'm not sure how it relates to your 8th gen.







You'll find the TECA harness hooked directly to the TECA.The part that sticks into the engine bay.You'll find it down below the brake booster.It's held in with a 10MM bolt.You can remove the bolt,pull and flip the harness over and probe the pin shown (with the key on) to test for power.Look closely and you'll see all the pins are numbered.Very handy.


The nice thing about the 8th gens trucks is,the TECA is removed from inside the cab,down under the drivers side kick panel.With the 9th gen trucks,it has to come out into the engine bay.This means the inner fender needs to be unbolted and pried down out of the way enough for it to clear.It's a bit of a pain.Super easy access in your truck as it comes right out inside the cab.I dunno how it's grounded but it may be under the kick panel with it.On the 9th gens in right there by the EEC-IV port on the fender.
This is,to say,it's main body ground of the TECA itself.As subford has shown,there's more than one in the whole circuit.

If subfords is specifically for the 8th gen years (89-91) then it appears to be the same.Pin 57 and the ground location looks to be in the same area.
I suppose if you were smart you would measure for resistance there at pin 20 to insure your getting 0 ohms too.This way you ensure power and ground are both @ the TECA before condemning it.If you don't have a meter you could jump a ground wire directly to the TECA body.
However I'm not sure the OD light glows dim when the TECA is'nt getting a ground (not that I know of).I know it does when it doesn't get power.Not sure if that's any indicator or not.Easy enough to make sure the TECA has ground and power at any rate.

 

I use pcm to refer to EEC/TECA/PCM interchangeably.

A common problem on the 87-91 trucks is they don't use a fuse to protect the pcm, in a over voltage situation the pcm has a surge protector that's a bit on the hard core side, if the voltage goes over the set point on the surge device it SHORTS the main power to ground, now being a fuseable link which is too strong to protect the pcm itself, it tends to burn off traces inside the pcm. A fuseable link only protects the wiring itself.

I would recommend to pull the pcm out and pop the covers off and look on the back side of the board around the plug area for burnt traces. Burnt traces can easily be fixed by soldering a piece of wire across the broken area.

 

That explains why his failed voltage regulator spike corresponds with his lack of power @ the TECA.

So like the 9th gens trucks use a fuse to feed the relay,he should add one anywhere in line, after his fusible link and before the relay too,to protect his new TECA.

 

OK here we go. I don't know the orientation of the pic you sent so...looking into the cap (connector 0from the driver's seat there are three irtical columns of pins

1. the top passenger side pin is hot w/ or w/o ignition on.
2. the second pin from the bottom passenger side is hot only when the ignition is on.
3.the 4th pin from the bottom in the center column is hot only when the ignition is on

I cannot for the life of me get the TECA to come out at all. I will try to remove the cover near the E brake or the fender skirt. I only have one working arm so this won't be quick.

 

Honsetly it's more of a issue with the design of the pcm then the fusing device, there is 2 runs of 14ga wire feeding the pcm and inside the pcm is maybe 22 gauge equivalent of copper trace, if that surge device triggers and can't hold the surge it tends to die shorted and burns the trace off.

Here is a pic of the trace that likes to burn in red. The circle area is the back side of the surge device.


Here is a top view of the surge device


Now if you want to try and fix it for testing purposes or to just run it and the trace is burnt, run a piece of wire across the burnt trace to fix that and using a meter on either resistance setting or diode check the black surge device to see if it's shorted, if it is shorted just cut it out and see if it works, it's not needed for the operation of the pcm and can be left out if you want.

 

[QUOTE=FORDF250HDXLT;17572906]I would test to see if power is making to the TECA from the relay now.

This is for 9th gen trucks.I'm not sure how it relates to your 8th gen.
[QUOTE]
Earlier you posted that the 9th gen controller retro-fits to the 8th gen trucks. if that's a plug-in why would you not know? Does the retro-fit require changing the connector?

 

Repairing the TECA is beyond me, besides I already ordered and paid for a new one. I just hope that's the problem. If anyone can further explain the pin placement in the TECA connector or my response above to what I found I would appreciate it.

 

I went so far as to take pictures and zoom in I can't find any numbers.

 

OK detective work is complete(I think). I finally got the TECA out it smells like an electrical fire!

 

Yeah right.Good point.She'll plug right in and work out good for ya.

 

That's a good thing, because that's what I ordered. But I will say that I called back over to Napa and confirmed that the one you listed in your early post fits 1991 (3 rows of pins). It does.

 

F4TZ-12B565-AA is the one for your truck it looks like.Appears to be A-1 CARDONE 736100 cross referenced.Based on a quick and dirty google search so don't hold me to it.

 

I Google searched it myself and also double-checked with Napa it's all good. Also I will say this to your credit. That Information from Transmission Exchange has been posted on four or five different forums by dozens of people and you and one other person are the only ones that give it credit for where it came from. It is absolutely amazing to me how many people have cut and pasted that and called it their own words. Plagiarism!
GOOD FOR YOU!