ECM Swap Issues

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Last to Know
Aug 25, 2008
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Ontario Canada
93 SHO converted from automatic to standard, but using all the automatics wiring system.

Car became harder to start, finally would only roll-over. Sprayed a shot of starting fluid and the motor would rock around, but would not start and run. Thought it was fuel issue originally, then proved it was a spark issue by doing the spark plug test.

Changed the Constant Control Relay Module (CCRM) and my fans came back, but still no start.

Took a chance and found a Engine Control Module (ECM) and proceeded to swap . I had to use extensions and universal joints to take the 11 mm bolt built into the connector, out. The AC tubing and large wiring harnesses keep you from seeing the bolt, let alone getting a socket on it.
Next, went inside and lowered the glove box door, and used a 7 mm socket and universal to remove the back brace of the ECM. Very tight location, and only could get finger tips on the back of the unit, and it would not come out by wiggling it. Found vice grips with a long nose, and wiggled it more, and it came out.
Then I forgot which way was up on the unit, (tabs are down) and had to look through the hole in the firewall to see the connector to verify.

I slid the unit into the space from inside the cabin, and the connector on the engine side fell out of the opening and dropped down. Took the unit out and spent a huge amount of time trying to get the connector back in the former position, but the same thing happened again when I slid the unit back in. So it put the brace back in and supported the unit. Went back to the engine compartment and with wires and screw drivers move the connector back into place, but could not get the connector bolt to enter the threaded hole in the ECM.

Back in the passenger compartment, took out the brace and pulled the unit out again. Looking through the empty hole in the firewall, I went back to the engine compartment, got the connector to center itself in the opening, and put wedges behind it to keep it in that location.
Back in the passenger compartment, I shoved the ECM back into position, and moved it in, as far as I could, knowing I was not going to push the connector out of the way as it was blocked with the wedges.

Back in the engine compartment, got the socket, swivel and extension and turned it by hand until it got some resistance. Went back under the dash and pushed it farther, went back out and turned the extension a few more revolutions until i hit resistance. Repeated this about 3 more times, then used the ratchet to pull it in more. I reinstalled the brace and I knew it was as far ahead as it could go as the brace bolt lined up with the provided hole.

All in all, not a satisfying experience as it took about 10 X longer than I figured.

If anyone has done this before, where did I go wrong? I am thinking the connector falling out of the firewall opening was the problem, maybe it was supposed to remain in place by having tangs that kept it fastened to the firewall. The AC solid lines really obscured the access to the connector. I don't know what, but something went wrong.

The new ECM solved the starting problem, and the rocking of the engine with the staring fluid was explained to me as the compression alone will fire the cylinders as the stuff is so volatile.


SHO Member
Nov 2, 2001
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va beach,va
I think rubydist has done this conversion?? I remember him at least commenting on this in an old thread. Try a message to him to point to this post


SHO Master
Staff member
Super Moderators
Jun 25, 2007
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Yes, I have done this before. It is a bit of a challenge to get the connector on/off the pcm, but I was able to do it with less jockeying around than what sperold has described.