Bad ECM?

Topic: Bad ECM? (Read 20955 times) previous topic - next topic

Reply #45 – March 14, 2015, 07:30:05 PM

Quote from: softtouch;446043

Sorry, I looks like your Signal Return (pin 46) is zapped. Signal Return is the logic ground for all the 5v stuff outside and inside the EEC.

To confirm it's blown, run the KOEO tests with the STI jumped to Sig Rtn. If blown you will get no codes not even the 11 good code.
Rerun the KOEO with STI jumped to ground. I think you will get some codes .

Someone fixed this on this forum a while back. He opened up the EEC and found where pin 46 entered the printed circuit board.
He traced the land pattern and found where it burned off. He even had pictures, I'll see if I can find the thread.

Alright, I will try these methods and let you know. I would very much appreciate that link to the repair.

Bad ECM?

Reply #46 – March 14, 2015, 08:59:15 PM

Could not find the link I remembered but I did find this on the corral forum. It shows the sig rtn land blown.
If you can find the blown spot you could try to solder in a small wire to bypass the bad spot.
http://i154.photobucket.com/albums/s276/slow88lx/mustangcomputer001circle.jpg

Bad ECM?

Reply #47 – March 14, 2015, 09:52:57 PM

Quote from: softtouch;446043

Sorry, I looks like your Signal Return (pin 46) is zapped. Signal Return is the logic ground for all the 5v stuff outside and inside the EEC.

To confirm it's blown, run the KOEO tests with the STI jumped to Sig Rtn. If blown you will get no codes not even the 11 good code.
Rerun the KOEO with STI jumped to ground. I think you will get some codes .

Someone fixed this on this forum a while back. He opened up the EEC and found where pin 46 entered the printed circuit board.
He traced the land pattern and found where it burned off. He even had pictures, I'll see if I can find the thread.

Alright, I will try these methods and let you know. I would very much appreciate that link to the repair.

Bad ECM?

Reply #48 – March 14, 2015, 09:55:34 PM

Thank you. I will open my ecm and take photos to post.

Bad ECM?

Reply #49 – March 15, 2015, 01:10:39 AM

Yep, this can be caused by a bad chassi ground by the battery. It forces the sigrtn ground to run through parts of the computer that aren't designed for that kind of load.

That small block ford no start write up i referenced you to has steps to check for this in the very first bit.

My buddy's third had a random dying issue. It ended up being both the fuel pump and that chassi ground by the battery. The connector corroded and was making an intermittent connection. Luckily we replaced the pump and ground wire and i out nearly 100k miles on it when i bought it off of him with no issues. His tps was reading 12v's before we found it.

Bad ECM?

Reply #50 – March 15, 2015, 01:34:30 AM

Quote from: Haystack;446072

Yep, this can be caused by a bad chassi ground by the battery. It forces the sigrtn ground to run through parts of the computer that aren't designed for that kind of load.

That small block ford no start write up i referenced you to has steps to check for this in the very first bit.

My buddy's third had a random dying issue. It ended up being both the fuel pump and that chassi ground by the battery. The connector corroded and was making an intermittent connection. Luckily we replaced the pump and ground wire and i out nearly 100k miles on it when i bought it off of him with no issues. His tps was reading 12v's before we found it.

Yeah I checked into that thread yet again. ( I referred to that for my no spark help) and I found a thread on how to troubleshoot the sig rtn. So I'm gonna try these things from Joel. I'll let you guys know.

Bad ECM?

Reply #51 – March 17, 2015, 02:40:52 PM

Well gentleman, I tried pulling the codes by jumping the Sti and sig rtn, but I got nothing but. Steady volt lamp with koeo. So I then tried pulling them by grounding the sti to ground, on the negative batt terminal, and I was able to pull 7 codes, and then 2 continuous memory codes. The 7 codes are as follows:
22- MAP out of range
35- EGR pressure feedback regulator circuit
51- coolant temp sensor out of range
53- TPS input out of range
54- ACT sensor
67- Neutral Drive Switch Circuit
95- Fuel Pump Circuit problem.
Then I had 9 seconds, followed by a blink, then 9 more seconds, then I got a code 95. Fuel pump circuit problem.
So, I found it quite obvious there was an inevitable issue with pin 46, just as Softtouch said he was afraid of. I figured since the sig rtn wire goes to the MAP, TPS, EGR, ECT and ACT sensors, and they all are throwing codes.....I decided to pull the computer. I opened her up, and sure enough, through the overwhelming stench of burnt electronic smell, the infamous pin 46 circuit was burned. (I'll put a picture up of it then) I took the voltmeter, put it on continuity check, and pinned the ends across the burned gap, just to make sure. Needless to say, I go a big fat O.L on my meter. So I think I will try to solder a thin 28 gauge wire across it, like I saw on the corral I belive it was. Any thoughts? Should I try mending it to save the $$ or should I take it to advance and get a remanned computer? Thanks for your continued help guys. I really appreciate it.

Bad ECM?

Reply #52 – March 17, 2015, 04:08:24 PM

Gently se the coating from the traces and lay your wire on them, solder in place...

Doesn't cost anything and you may get lucky...

Bad ECM?

Reply #53 – March 17, 2015, 06:48:50 PM

so what is the root cause here,, improper 02 harness for Mass air or what?

Bad ECM?

Reply #54 – March 17, 2015, 08:43:17 PM

Id say not running the ground between the chassis and ecm. It forced the sigrtn load to run though pins 20 40 and 60 and puts excess load through the traces and eventually burns it up.

Or at least that's how i remember it being explained to me a few years ago.

Bad ECM?

Reply #55 – March 17, 2015, 08:59:34 PM

I'm going to try and go back over tomorrow and see what happens. I'm worried I'll blow it again. Could it have been a bad O2 harness? I'm using a manual mustang harness. Before I plug in the computer, should I check for voltage on pin 46, with key on, cranking, clutch in, clutch out, and off and all that? What voltage is needed to burn up the trace? More than like 1 volt? Will milli volts burn it? Here's a picture of the wire my father in law helped solder in.

Bad ECM?

Reply #56 – March 17, 2015, 09:03:09 PM

Bad ECM?

Reply #57 – March 17, 2015, 09:53:30 PM

wow,, I think I heard someone yell all the way down here in west by god "now burn up you sumbych"

that sure as hell will do it.. hope it works.

Bad ECM?

Reply #58 – March 17, 2015, 10:10:24 PM

What's the black Mark on the trace right below?

Also, there is a difference in auto and manual computer wiring to the o2's. I don't remember exactly what it is though. Id check for correct orientation of the pins from the o2's plug to the corresponding pin on the computer plug to make sure the wiring is correct.

Bad ECM?

Reply #59 – March 17, 2015, 11:08:04 PM

Quote from: Haystack;446267

What's the black Mark on the trace right below?

Also, there is a difference in auto and manual computer wiring to the o2's. I don't remember exactly what it is though. Id check for correct orientation of the pins from the o2's plug to the corresponding pin on the computer plug to make sure the wiring is correct.

Nope not so, o2 pin out is identical on stick or auto, MAF or SD... My o2 Wiring harness is from LSC Lincoln & I've swapped a A9P, A9L & C3W back and forth in my Bird & never had a issue... If o2 connector is pinned incorrectly(12v on signal return) or sensor shorted internally, that can damage ECM, as could a mis wired MAF meter...

The TAB & TAD solenoids are pinned differently between MAF & SD, are four extra wires for MAF meter and one for the fuel pump monitor but that's about it...