ICM connector design flaw

[Anthony]

Maybe this will help someone. I finally pinpointed the culprit behind an intermittent stalling, rough idle, lack of power situation. It would run perfectly smooth most of the time, until some random moment when it would start acting up (usually when giving someone a ride 😂🤦‍♂️).

 

It didn't set any codes for a while, but did eventually set E042: open spark timing communication circuit between the ICM and ECM. This caused the ignition to spark at a default 10 degree advance at all times, regardless of the situation.

 

Upon inspection of the ICM connector, I found all the female tangs wide open, in such a way that the pins would likely not be making contact, or contacting intermittently. Also, the screw had been tightened so tight that it split the connector in half and made a 1/8" impression in the plastic. 

 

After splicing in a new connector, I noticed that it is very hard to tell when to stop turning the bolt. The way it's designed, it has no discernable stopping point because of the rubber gasket inside the ICM. This is a very poor design, in my opinion. I don't know what the solution is, except to count the bolt threads and the number of revolutions of the bolt as you're turning it, to make sure you get a good connection without breaking the connector.

 

There is a section in the service manual on how to remove the tangs from the original connector with a special tool, reform and reinsert them, if anyone is interested. It could very well clear up a driveability issue for you, without replacing any parts.

 

Photos showing how worn out the connector was, at only 21K miles:

[2seater]

Some people remove the internal cushion for the reason as stated. Once the bolt has been cinched down to the point of deformation and then destruction, there isn't a cure for that, except as you have detailed. I am pretty sure the design is for the bolt to be a retainer, not a method to pull the connector together. 

[Ronnie]

Interesting that what I assume is the new connector, has wires that are all the same color. Plus it appears to have two extra wires in it. I'll bet that will be hard one to troubleshoot.

[Anthony]

2 hours ago, 2seater said:

I am pretty sure the design is for the bolt to be a retainer, not a method to pull the connector together. 

That is what I've heard as well. However, I was unable to insert it without turning the bolt at the same time, because the threaded end of the bolt has a starlock washer that prevents the connector from moving independently of the bolt. I presume this is to avoid losing the bolt after unscrewing it.

Edited December 15, 2023 by Anthony
Focused quote

[Anthony]

2 hours ago, Ronnie said:

Interesting that what I assume is the new connector, has wires that are all the same color. Plus it appears to have two extra wires in it. I'll bet that will be hard one to troubleshoot.

It was also fun to wire because the first time I didn't notice the 2 extra wires and just connected them in order 😂. In addition to them being all white, it also didn't come with the flimsy black plastic cover, which was absolutely destroyed, and I assume unobtainable. I tried to salvage it by melting the broken pieces back together with a soldering iron and fashioning a makeshift hinge out of electrical tape. 

[2seater]

14 hours ago, Anthony said:

That is what I've heard as well. However, I was unable to insert it without turning the bolt at the same time, because the threaded end of the bolt has a starlock washer that prevents the connector from moving independently of the bolt. I presume this is to avoid losing the bolt after unscrewing it.

That is true. It is a sort of push-snug bolt-push-snug bolt push sort of pattern. I had forgotten about that😖

[Anthony]

On 12/15/2023 at 11:56 AM, 2seater said:

That is true. It is a sort of push-snug bolt-push-snug bolt push sort of pattern. I had forgotten about that😖

You're right. After you said that, I went back and tried it again. I found out that I could just push it in a bit, then turn the bolt by hand, push it and turn it again, and it fully seated. The socket wrench was not even necessary. So then I just snugged it up a bit with the wrench and that was it. Thanks for the tip.

[Nailhed66]

Replacing the connector and splicing in a good length of new  wire as you’ve done is what solved a persistent EO42 issue on my’88. The connector that was replaced appeared fine and I suspected a bad wire as it was routed so close to the lower radiator hose. Lots of electrical tape and re routing the wire away from the hose seems to have done the trick. FYI, I left the pad in place and only tightened it until it felt seated and secured. 

[2seater]

The touchscreen cars vs the non are completely different under the hood. The earlier cars routed around the front of the car low by the frame. The later cars had the engine wiring over the top from the firewall to behind the power steering pump. The later cars would seemingly have a more direct path, and it is, but every one of the late front engine (crank and cam sensor) harnesses has had areas inside the loom where the wire insulation was crispy and missing. Thirty five + years has taken a toll.

[Anthony]

On 12/24/2023 at 11:04 AM, Nailhed66 said:

Replacing the connector and splicing in a good length of new  wire as you’ve done is what solved a persistent EO42 issue on my’88. The connector that was replaced appeared fine and I suspected a bad wire as it was routed so close to the lower radiator hose. Lots of electrical tape and re routing the wire away from the hose seems to have done the trick. FYI, I left the pad in place and only tightened it until it felt seated and secured. 

E042 came up again today.  I'll try this Deoxit D5 on the connections at the ECM next. It says it removes oxidation and adds a coating that reduces intermittents and arcing. From what I've read, the coating is conductive when heated but insulating when not, so it makes it a stronger connection where the terminals meet, but won't cross over the plastic to short out other terminals. 

 

The car still runs weird sometimes even without setting the code. I suspect that the EST circuit connection is intermittent, so the ICM isn't always getting all the spark timing pulses from the ECM; it might be that only some of them are coming through.

[Nailhed66]

I found that clearing the code and doing a battery disconnect reset will briefly give false hope as the engine will run as normal for a short period before the ECM puts it back into default spark mode and you get the dreaded ”electrical problem detected” message. I was prepared to replace wires all the way back to the ECM. Using the full length of wires that came on the new connector surprisingly solved my issue. Of course it could be anything from ICM to ECM and there are scientific methods for troubleshooting, but I chose process of elimination. Please continue to keep us posted on how this works out. 

[Anthony]

Well, I didn't even get to using the contact cleaner because I found bypass circuit 424 shorted to ground inside the ICM, by testing unplugged ECM terminal BC7. Unplugging the ICM eliminated the ground short. This ICM is only a few months old. It did run perfectly when I first installed it. I wonder if the loose connection ruined something inside it. Who knows. I was pleasantly surprised to find out the ECM connector is fairly easy to access for testing purposes. I only drew blood once.

[Anthony]

New ICM has the exact same resistance as the old ICM from pin B (bypass circuit) to the case ground of 9.6 ohms. So I put the old ICM back in and did the ground short test again, this time using a test light as the manual says to do, instead of a voltmeter, probing ECM harness BC7 and the other end to 12V. The test light did not come on. Voltmeter still showed voltage of 11.4V. 

 

I feel somewhat led astray by the service manual because in the intro to the electrical section it says a voltmeter can be used anywhere a test light is called for. Apparently that is NOT the case, because even though the voltmeter read 11V, there was not enough of a ground to light up a test light. So maybe a resistance of 9ohms to ground does not indicate a short.

 

I did use the Deoxit D5 on the ECM connections. I also found the battery cable's negative terminal stripped, so I replaced that. Drove the car for 8 miles without any problems. I don't know if I fixed it or not. I guess time will tell. 🤷 I'm afraid to return the ICM before I know for sure, because that could invoke Murphy's Law 😳 in addition to Ohm's

[Ronnie]

1 hour ago, Anthony said:

The test light did not come on. Voltmeter still showed voltage of 11.4V. 

I'm not an electronics expert, but most likely the ICM uses SCRs to trigger the coils to fire. The SCRs may leak some voltage, which isn't unusual,  but still not allow enough amperage through to turn on a test light.  Maybe that is the reason they recommend using a test light. My comments are based on the ignition system on Evinrude boat motors I've owned that use SCRs in their electronic ignition systems.

[Ohjai]

"The test light did not come on. Voltmeter still showed voltage of 11.4V"

 

This indicates to me that hte 12 Volts are there, the reason the test light did not come on is there was no return path.  The ground side is open.

 

[Anthony]

This issue was finally fixed by replacing the ECM. I tried two from rockauto at $125 each that were both bad. Got one on ebay for $25 and now the car runs like new again. No code 42 either so far 😀🤞