Fixing a Key Fob That Has Been to the Cleaners.

I was asked to have a look at an early 2000's GM key fob that had gone through the wash. It wasn't working but previous experience with key fobs, had shown them to be pretty resilient to such things. I was confident that I could probably get it working again.

Step 1: Taking Apart

This particular style of key fob is very easy to take apart, with no screws involved. Just take a knife blade and gently pry apart the two plastic halves of the shell of the key fob. The two halves will come apart as shown in the picture.

Step 2: Gently Pry the Battery Out of It's Holder With a Blade

Gently insert a knife blade under the battery and pry it out of it's holder. Note how the battery is mounted. There is a negative and a positive. In the photograph you are seeing the negative side facing up. The other side is clearly marked as positive and has the name of the manufacturer on it. Before you put the fob back together, bend the metal finger a little bit so it touches the battery with more force. If you have a meter, check to make sure that the battery is over three volts. My measurement was 3.15 volts. You can also replace the battery if you want to.

Step 3: Take Apart the Other Side

Take apart the other side of the fob separating the three parts, holder, rubber button assembly and circuit board. At this time, bend up slightly the little metal fingers on the circuit board that make contact with the battery.

Step 4: Wipe Down Every Surface

Wipe down every part and surface with Methyl Hydrate or Isopropyl Alcohol. This should get rid of any residual detergent which could interfere with the operation of the device.

Step 5: Before Reassembly Allow the Parts to Dry for a Few Hours

Be sure to allow the parts to dry for a few hours before reassembly. This is especially important for the carbon touch pads.

Step 6: Reassemble Key Fob in Reverse Order

Reassemble key fob in reverse order taking care to make sure the positive terminal of the battery is facing the plastic case.

Step 7: Put Everything Back Together

Put everything back together and test if you have the car nearby. Unfortunately I didn't and I had to test using the next strategy.

Step 8: If You Don't Have the Car Nearby You Can Test With a Spectrum Analyzer.

I didn't have the car nearby to test the key fob so I needed to test for a signal. I looked up the FCC number for that key fob and got the frequency it broadcasts on. I set up the spectrum analyzer for approximately 315 MHz as the center frequency and put a small antenna on the input. I held the key fob a few inches away from the antenna and pressed one of the buttons of the key fob. The center of the display shows a strong carrier with two sidebands typical of the type of modulation used by most remote key controls of that generation. Knowing that there is a strong carrier signal on the right frequency and seeing that a signal is being encoded on it, there is a high probability that the unit is working.



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    9 Discussions


    1 year ago

    awesome fix. Can you explain how to find the fcc number and how to get the frequency it broadcast ? I am very interested in learning how to do that. Thanks.

    4 replies

    On the back of the key fob is an FCC identification number. Go to this FCC website and put the number into the proper column in this website. It should tell you the manufacturer and frequency. Most North American made cars operate on a frequency of 315 MHz and 433.92 MHz for all others. Here is the FCC website:

    Maybe yours is an aftermarket one but it would still be on 315 MHz if it's a North American car and 433.92 MHz if it's not.

    ThriftStore Hacker

    3 years ago

    if the unit still isn't working the programming may have been reset. simple fix. just Google gm key fob reprogramming :)

    1 reply

    3 years ago

    Isopropyl alcohol works great for small electronics like this. These things are incredibly resilient; I must have washed mine a dozen times now, cleaning it as you describe after has worked every time. Never had to replace the battery yet, and it goes to a 2003 F-150...

    It's worth noting that some (mine) don't come apart so easily - they can be sealed with glue and I suppose some may have screws. I used super glue to reseal it a few washes ago, thereafter I've just let it dry on its own for a few days and even threw it in the dryer with my clothes for a few minutes twice. Still works. Still unlocks from 50+ yards inside a building.


    3 years ago

    I was once on a vacation in Hawaii when the keys went to the seas. It turns out that the sea water had gotten into the battery, which could have easily broken down its chemicals. Sure enough, I replaced the battery and the keys were up and running again.