Toyota Corolla cleaning electrical contacts

My 2005 Toyota Corolla had water damage few years ago. The car runs great. No issues and I love the car. But, the SRS light is constantly on since that water damage.

Toyota dealer wanted half of my life’s earnings to diagnose and fix it. They said, there is no communication to the SRS module. It would be about $2000+ to try to replace the module. Then, they would know if that worked or not and maybe twice more to finally fix it (maybe).

Some time back, I removed the SRS module from the car to see what is going on. I was thinking of sending it in to one of those Internet places where they repair or program the module for like $50. I saw some green oxidation on few pins on the module. I am assuming that there might be some oxidation on the female connectors too (i saw some green stuff on the female connector too). If oxidation is present on the female connectors, swapping the module with another does no good. Maybe, the only problem with the car is that the oxidation on the connectors is preventing any communication with the SRS module.

I managed to get the male pins clean, but cleaning the female plug remains a challenge to me. I cleaned with some vinegar solution first. Let it sit for like 5-10 minutes. Then neutralized the acid with a solution of baking soda and alcohol (I used alcohol because, it dissolves baking soda too, but evaporates off). I didn’t like it because it left the baking soda on the pins. Since these connectors need to make a good electrical connection, the left over baling soda might do more harm. I finally rinsed the whole module and air dried it.

I am a newbie to the world of diy. I benefitted from the wisdom of many people on this forum on several projects in the past. I am hoping that someone would share some of their experience where they solved a similar problem.

What I have in mind at this point are:

  1. Use a fine wire to laboriously scrap the inside of the female connectors. Maybe, I might be able to remove some oxidation. This method doesn’t look promising to me because what I need is a tiny file, the size of a 20 awg wire and I don’t have anything like that (unless I can think of making one. I might try to make some lines on a thin wire and use it as a sort of file.

  2. Spray a mixture of vinegar and salt in to the female connector, let it sit for 10 minutes and then scrap with that wire for a better result. Followed by spraying a solution of baking soda mixed in alcohol.
    The challenges that I am thinking there will be are that, since the holes on the female connector are very narrow, air bubbles might prevent the vinegar or baking soda solution from going in. Also, removing the vinegar or baking soda might be challenging, I could even clog up the holes, defeating the purpose of this project.

  3. My understanding of high school chemistry is that, it takes some kind of an acid to react with the oxidation. But, I have seen several people (on Internet diy videos) spraying organic solvents to remove oxidation, which is an inorganic compound. It doesn’t sound logical to me, but I am even thinking of spraying some MAP sensor cleaner on the female connector. Not sure if it will work or not. I don’t want to spray brake cleaner, because it will not be good for the plastic.

  4. If nothing works, I am thinking of going to the junkyard and find a similar car, cut off the connector and attempt to rewire it on my car.
    Looking at the tight space, short wire and the million connections, I am not confident if I can pull that off.

This is everything that I have planned. Each plan has a negative side, which makes me to second guess myself.

What do you suggest I do in this situation? Thanks in advance for all your suggestions.

All you need is something like this.


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The contact cleaner specs says, it is a cocktail of volatile organic solvents suitable for removing oil, water and dirt. How will it remove a layer of green copper oxide? (Just wondering…).

I heard of a product called deoxit. It is very expensive though. Any thoughts on this product?

When we wash boards or electrical assemblies at work, we use a cocktail of DI water and various cleaners and surfactants. The last thing you want is conductive or corrosive elements deposited under or around components. The good news is this board is probably conformal coated and somewhat protected.

All copper is tinned or electroplated to protect it from oxidizing. Using mechanical abrasion will remove any protective coating and it will oxidize even faster next time. The bad news is you already have copper oxide…

Are the female pins inside a wire harness connector?

Deoxit is not that expensive. sells several versions of it starting at $11.50. I’ve used it often on delicate electronic equipment with excellent results. As for the female contacts you might try dental “Go Betweens”. Gum Proxabrush Tight is very small. Its bristles are made of nylon and won’t scratch the contacts. just spray the contacts and brush.

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No matter what you do to clean up the contacts, considering how badly the car was apparently flooded, you will be dealing with various mysterious electrical issues for the remainder of the time you own this car. Now might be a good time to bail out ( pun fully intended).

Do not use any corrosive chemical. And definitely don’t attempt to cut off the connector and splice the wiring harness from a junkyard car, unless you have experience doing this type of work properly. You will make the problem worse.

I use a paper towel with 90% isopropyl alcohol to clean electrical contacts. If really corroded, I use a pencil eraser or fine-grit sandpaper first.

After cleaning up the connections on both ends, if that doesn’t solve the problem, you can try a SRS module from a junkyard to see if your module has failed. If a used SRS module doesn’t solve the problem, I’d ignore the warning light and always wear my seat belt (which you should be doing anyways).

The female pins are in a wiring harness and there is no room for a wire brush to go in.

I am not worried about cleaning the module itself. I have disassembled and cleaned it couple of times. The male pins on the module are relatively easier to clean.

The female pins are on the car. Very short wire. Tight space and the holes are no bigger than 18-20 gauge wire. So, using sandpaper or such methods are difficult.

Any idea what is in deoxit? Some sort of an acidic compound, maybe?

The Gum Proxabrush Tight will easily fit in an 18 gauge hole and probably a 20 gauge hole. Deoxit is made for delicate contacts such as potentiometers and switch contacts. You can get a description of both on Amazon.

Deoxit is a professional contact cleaner. In the HVAC industry, we use a similar product made by Nu-Calgon. It is NOT acidic or corrosive. It contains a HFC propellant and a blend of volatile hydrocarbons which act as a solvent. In the past, CFC and HCFC solvents were used for this purpose.

Have you tried to trace the the wiring harness to see where it connects to the rest of the car’s wiring? You may be able to replace the entire thing without resorting to butchery.

Replacing the harness is my last resort. I have to see how much of the car I need to dismantle to get all wires out in tact. I am gonna try one of the contact cleaners to see if that works. If not, i need to think of replacing the haress.

I’m just shooting in the dark, but would a rosin based flux used for soldering electronic circuits be helpful here? Maybe put a touch of it on each male pin and then push the connectors together?

Take this for what it’s worth - not much. I’m not trained at all in this area and I’m just guessing.

This is the type of product I’m thinking about: Rosin flux

There are many flux formulations. All are corrosive to a point but some are extremely so. You’d normally never want to leave flux on the metal, it will corrode it over time.

That wiring harness is surely dug in like a tick into the mass behing the dash. I’m adventureous but would never attempt that. It would be easier to buy the correct pin pusher and extract the pins one by one to clean or replace them.

Before I did any of that, I would use a contact cleaner like one mentioned. You should be able to back probe the connector to ohm out the connections if you disconnect the battery first…

For the female contacts, use a paint brush, acid brush (flux brush) or a chip brush. The bristles will not damage the pins. Check your local electronics stores or go the Fry’s website and get some alcohol that is at least 99.5% pure.

BTW MAF cleaner is alcohol.

Now for the part that is going to freak out most of the people here, coat the pins with a dielectric grease. You can use the grease sold in little packets for spark plug boots. Many people are unaware that dielectric grease is actually conductive in a very thin film as you would get in a metal to metal contact. But any thicker than that, it insulates and protects.

I did some experimenting with corroded pennies using various cleaners. Alcohol and MAP sensor cleaner does nothing to the green compound of copper. Vinegar with salt cleaned out most of the corrosion in a few seconds. I read somewhere that the chloride ions in salt and the acetic acid for hydrochloric acid, which makes it a better cleaner. Apparently household bleach also has chloride ions, so I added a few drops of it too. The pennies did come out pretty clean. Areas with the heaviest oxidation still needs an abrasive.

I am still deciding whether to use this on the wiring harness or something store bought. If I use this cocktail, I could neutralize it and then wash it off with alcohol, which would drive out the water from the tiny holes. I could use compressed air to dry everything out.

Doesn’t dielectric means an insulator? It always confuses me why dielectric grease is recommended on spark plugs where a good connection is needed. I am thinking of putting some on the pins before connecting. Will it mess up the connection?

Since the central console in the car is off, I was looking around at the various electrical connections and noticed that there is corrosion on another wiring harness right across the parking brake. When I tried to clean the pins, one of the pins broke off; it was corroded so bad that the base of the pin just came out. Now my option for fixing this would be to cut the wires and get another wiring harness. Instead of getting a wiring harness, can’t I connect both ends of the wires together and insulate them?

Now I can see why people say water damage is really bad for a car. So many hidden connections get corroded away abnd we’ll never know what is causing various problems.

I’d start w/trying some of that CRC contact cleaner. I’ve seen it at Home Depot, costs less than $10. If I wanted to experiment with something else the 99% pure alcohol idea above is a good one, and I’d also see how acetone affects the corroded pennies as an experiment of what’s possible. Is there a reason you aren’t sending the module out for a $50 repair as you mentioned might be possible earlier?

I think you’re on the right trail with your experimentation, and your questions. Dielectric grease is essentially non-conductive, and it’s used to lube the spark plug cover boots, which you certainly don’t want to be conductive or sticky.

I searched Ebay for jeweler’s files, to see if there’s something abrasive and thin enough, and there are cheap sets from China, but the sizes are difficult to figure out. If you had a thin piece of metal the thickness of a male connector could you rough it up a little and then use it as a substitute file? On old motorcycles I have sprayed connector cleaner all over both the male and female connectors and then pushed them together and apart a bunch of times while they were still wet, and it has helped, but recently I had to replace an entire wiring harness because the old one was too far gone. Easier on a motorcycle, of course.

I think acetone might melt the plastic on the wiring harness. So, keeping that out. Tried alcohol, but the tough oxidation seems to need an acid and some scraping. I wonder what chemical is in those products that claim, spray it on and let it evaporate the oxidation. Volatile acids?

I bit the bullet and finally brushed in a solution of white vinegar, salt and bleach in to the female connectors of the wiring harness. Let it sit for a few seconds, used a tooth brush to push it in and scraped a bit. Then cleaned it out with a damp towel and neutralized with baking soda solution. Then used some alcohol to try to repel the water out. Used compressed air to blow out the liquids. This was two days ago.

It had been raining and damp for the past couple of days here in Houston. I didn’t want to take a chance with connecting the wiring harness to the srs module if there is moisture still in it.

I connected everything back, but the srs light is still on.

Could it be possible that now there is connection between the module and harness but the module needs to be reset?

How does this work? Once the srs light comes on, even if it is because of moisture damage (like in my case), does the srs module need to be erased of the error or will it go off on it’s own once the problem is fixed?