Cleaning the J3 Connector on the PCM.

[Power Hungry]

We frequently get asked, "How clean should the PCM connector be when installing a chip?" The answer is "Really clean!" However, there always seems to be some confusion as to what is really clean and what is too clean. Hopefully this will provide some insight.

When the PCM is manufactured, they are dipped in silicone in order to help seal the components and prevent moisture contamination and corrosion. When installing a chip, this layer of silicone needs to be removed in order for the chip to make a solid contact with the circuit board. Failure to adequately clean the PCM contacts can result in a no-start condition, stalling while driving, poor performance, and even damage to the PCM and/or the chip.

Okay... so we've established that the connector should be really clean. How do we clean it? The best method, if you have one available, is a BRASS scrub brush (for example: Brass Mini Brush #46630 by Hyde Tools at HardwareAndTools.com). This is the ideal tool for cleaning because it removes all the silicone and does not damage the board or any components and does not remove the tinning from the contacts.

In know that Scotch-Brite pads are included with the chips, but Scotch-Brite should ONLY be used for a light polish once all the silicone has been removed from the edge connector. This includes removing any silicone from in between each finger on the connector. In the absence of a small scrub brush, a toothpick works really well for these areas. Once the silicone is removed, then you can use the Scotch-Brite.

After you are done cleaning, there shouldn't be ANY copper showing. The contacts should still have a fully silver hue. Visible copper is an indication that you've removed the tinning on the contacts and you are more susceptible to corrosion on the contacts which will compromise the connection.

Another thing to keep in mind is that most standard card edge connectors are designed to accept .062" to .064" thick circuit boards. As it happens, OBS computer PC Boards ('94-'97) are .062" thick so there is little concern regarding connection problems. However, '99 and later computers are only .050" thick and can present a significant connection problem, especially if you remove .001" to .002" of the tinning from the edge connector.

In the event that the contacts have been overly cleaned, it is not a lost cause. Any experienced electronics or TV repair shop should be able to re-tin the contacts which will help provide a better surface for the chip to grab on to and eliminate connection problems.

Here are a couple examples:

Before Soldering (click to enlarge):


After Soldering (click to enlarge):


Pay particular attention to the slightly raised contacts after soldering. They are smooth and slightly rounded and are about .008" thick. Counting both sides, this helps make up the difference in board thickness that the edge connectors are expecting. Also, if you look closely, you can still see specks of silicone still left in between each of the contacts. This was after using only a Scotch-Brite pad to clean the connector. (I couldn't find my scrub brush!) It obviously doesn't get all the silicone from between each finger in the contact. Again, a toothpick is excellent for removing these remnants.

Your local Ace hardware usually has the little brass brushes in the paint department for a buck or two. It is worth the investment if you happen to be by one. If not, then just take your time with the connector and carefully remove the silicone before going at it with the Scotch-Brite pad. A little patience here can save a lot of aggravation down the road.

Hope this helps.

[Highbeam]

I hope it is okay to add to this sticky. Before installing my chip I found very little guidance, especially with pictures, about this critically important step of cleaning. Only warnings that you can destroy the chip and/or pcm if you don't do it "right", yikes!

I have large hands and the only difficult part of getting the PCM out was getting my fat hands down near the 10mm screw on the wiring harness connector. Go in from above between the hydroboost and the wiring harness.

So you see the needed tools in the bench pic. All you need is the brass brush from home depot, toothpicks, and your thumbnail. I was happy to have my compressed air nozzle to blow away chunks too. No liquid solvent was needed.

You won't be able to get the green circuit board out of the one half of the metal case. This means that one side of the PCM will be harder to clean. It won't look like a card inside your computer.

Start by using your thumbnail to scrape the silicone off of the top of the contacts, both sides. You can't hurt anything with your thumbnail. It feels gritty like scraping clear silicone sealant from glass or a countertop after you install a sink. You will only really be able to scrape the tops of the silver terminals clean.

Then hit it with compressed air to blow away the junk. The more often you blow away the junk, the less time you will waste stirring the junk around. It is hard to tell when you are done scraping when the scraped silicone is still on the PCM.

Then Scrub both sides with the brass brush. I was assured that the brass brush would not be able to remove the silver stuff from anything or damage other parts of the PCM. The silver stayed 100%. I'm not sure that the brush helped as much as the next step though.

Toothpick. The longest and hardest part is removing all the silicone from between the silver contacts. This area is recessed so nothing can get in there except a tool and a toothpick can do no damage but is quite good at removing the silicone. The one pic shows my progress with the toothpick, I started on the right and moved to the left. Blowing and scraping until only the matte black background of the PCM card can be seen. You will know when you have it clean since it is all the same shininess and smooth. Keep blowing it out and scraping.

So then go back over everything with all of the tools. You may did like I do and lose fingernail by scraping. The cheesegrated fingernail looks like silicone so you may think you are getting more but it is just your fingernail coming off.

The very last step is to use the scotchbrite pad included with your chip to scuff the silver contacts. This puts fine scratches into the silver to make good contact but also allows you to verify that you have them clean. If you don't see fine scratches for the full length of the silver fingers then you need to scrape that area with the toothpick.

The scotchbrite pad is the only thing described above that can damage your PCM so just barely use it a tiny bit at the very end.

Here are some pics. I believe that this is what the PCM is supposed to look like.

Also, the finished product. Chip works great with no hiccups. The most noticable thing for me was the transmission shifting was excellent, fast but no bang.