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ECU and wire harness corrosion

5963 Views 6 Replies 4 Participants Last post by  iyapojones
I have been having all kinds of issues with my ATS 2.0T with check engine lights and things not running right. One of the lights I got was for the cam shaft position sensor. I took it to a mechanic and he determined the sensor was bad because the computer was saying it was giving off low voltage or something along those lines and replaced it. This didn't help, so I took it to the Cadillac dealership, which I probably should have done to start with.

They found that the return hose to the coolant reservoir was leaking. I knew I was losing some coolant, but I would just top it off occasionally. Bad on me, I know. I should have fixed it. This leak is apparently really common with the ATS and Camaro. Unfortunately, the ECU is right below the "Y" in the line that was leaking. This caused corrosion on the bottom connector on the ECU as well as the plug on the harness.

The dealership wanted $2,200 to replace the ECU, splice in new wires to the harness, and repin the connector. I decided to to try to clean the ECU and the connector myself. So far, it seems to be doing much, much better.

I made a video of my adventures with this and figured I would share if with you all in case it might be helpful to somebody else. Moral of the story, fix those daggon leaks...

Here is the video if anyone is interested. I am not a mechanic and if I did something, or say something dumb, please leave a nice comment correcting me for the sake of anyone that views this video. Thanks!

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Nice repair and a good reminder of how a competent owner can save a lot of money by tackling a repair like this one and that is a nicely made video. A couple of hints for the future:

1. I got interrupted a few times while watching and maybe I missed it but remind people to always disconnect the battery negative terminal cable before this kind of work. It is really easy to cause damage to the ECU when you are dealing with conductive corrosion when you are pulling connectors from the ECU. After disconnecting the battery, you will need to do the throttle relearn procedure in the owner's manual (fast and easy).

2. WD-40 is an excellent flushing agent for getting the worst of the initial contaminant out of the connectors. It works very well for cleaning out electrical connector assemblies but use caution because it is flammable. It does a good job of dissolving most corrosion products and it is inexpensive enough to use for a complete flush. After using it to remove the majority of the corrosion products, then use regular electronic cleaner for the final step.

3. The soft bristle brush is fine if used lightly but be careful with any other brushes because the contacts are plated and the plating is easily damaged by any sort of aggressive brush, ditto for bending the contacts. This is a case where you want the cleaner to do the work.

4. We are coming up on the winter dry season so if someone tackles this later, beware static electricity. The ECU has some protection against this but caution is advised.

5. A low viscosity dielectric grease like you used works fine with connector contacts. It reduces the required mating force reducing the likelihood of bent/stressed contacts and will be pushed out of the way so it won't insulate the contacts. NOTE: Always use good quality grease like you have in the video, I have seen cheap import stuff that become conductive when it gets mildly contaminated (which happens in normal use, it is what a good dielectric grease helps to avoid). I had an antenna installation issue several years ago where the dielectric grease in combination with the metal contact actually acted as a battery producing a small offset voltage completely disrupting the controller feedback system. Thorough cleaning followed by application of a quality grease cured that bizarre issue which resulted in a controller constantly falling out of calibration.

Congratulations on a successful repair!

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Feel free to copy and paste it. You really did a great job with the video, informative and concise. Too bad most Youtube "how to" videos don't go so clearly from problem through process to solution like you did.

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