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ECM grounds by SemperFi18
Started on: 10-05-2021 10:02 PM
Replies: 5 (96 views)
Last post by: Dennis LaGrua on 10-09-2021 04:26 PM
SemperFi18
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Report this Post10-05-2021 10:02 PM Click Here to See the Profile for SemperFi18Send a Private Message to SemperFi18Edit/Delete MessageReply w/QuoteDirect Link to This Post
Okay guys, I think I have it narrowed down for my issue. I think I have an ECM grounding issue. I've read other posts and found where guys say they go, problem is I don't see the wires.

Other than the main ground, the braided chassis to block and the tranny plus the deck lid I don't see anything.. I have a ground through the starter bolt, green and black wire.

Terminals D1 and A12 on the ECM look a little blackened, I have no shorts between any pins other than grounds to grounds. Where are these damn ECM grounds? I don't remember taking off any other grounds during the rebuild other than the mentioned ones...
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olejoedad
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Report this Post10-06-2021 08:02 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
The ECM is grounded to a bell housing to block bolt/stud above the starter.
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theogre
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Report this Post10-06-2021 09:56 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
ECM has Several "grounds" only 1 or 2 are real grounds. Others are return lines for ignition and O2 sensor that must be good.
Tan O2 "ground" bolted to block.
ECM ignition "ground" is connected to the ignition.
See my Cave, Ground "Myth" notes

for ends bolted or screwed to whatever... clean/fix and coat w/ silicone or brake grease.

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SemperFi18
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Report this Post10-07-2021 02:58 AM Click Here to See the Profile for SemperFi18Send a Private Message to SemperFi18Edit/Delete MessageReply w/QuoteDirect Link to This Post
Answered my own question after looking at a schematic and realizing I was being stupid and hastily hooked up the starter.. Guess what wires are right by the starter?? The grounds for the ECM and O2. So hopefully this helps someone in the future. If you did a rebuild on a 2.8 and your having ECM problems, pop down by the starter and see if you hooked up a green/black bundle and brown/black bundle on the starter lug.. ya know cause they fit perfect.

I took that section apart quickly when I removed the engine, pay attention to the harness in particular when doing a rebuild. Take notes, take pictures and go slow. Luckily I didn't fry the ECM, just melted a few wires, simple fix but a lot of stress. These are the most frustrating cars yet the most rewarding, don't know what it is but their like an addicting puzzle
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olejoedad
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Report this Post10-07-2021 08:02 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
There is an adage among mechanics....

"Know how to reassemble before disassembling."

It's very helpful to keep in mind.
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Dennis LaGrua
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Report this Post10-09-2021 04:26 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Grounds are critical to proper operation. My 3800SC had developed a random misfire and was setting an 0300 code. I suspected that it was the coil pack or ignition module. On a hunch I removed the coils, module, cleaned the mounting surface. Then coated with conductive grease and ran a dedicated 16 ga ground wire to the mounting bracket. Started it back up, the problem was gone and the engine ran like new.

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