How Car Keypad Locks Work

Pioneered by Ford, keypads let you lock, unlock without keys

Pioneered by Ford, keypad door systems began appearing on high-end car and SUV products in the early 1980s. Ford took advantage of the then-new digital computer revolution – the automaker was one of the first to adopt digital technology for car/engine control – to add the keypad feature. Keypads may be located on the bottom of the driver’s side window from or along the driver’s side pillar. Keypads illuminate when you touch them so that you can enter codes.

How keypads work

Keypads work by generating digital code sequences. The codes are sent to the security control module, the computer that controls things like locking the doors, locking the trunk, setting and arming the alarm system and such.

The security control module accepts the code sequences, decodes them and generates the proper voltages for the door lock actuators. In turn, the voltages activate door locking and unlocking. The keypad also produces codes that will:

  • Activate memory seat features
  • Unlock the trunk
  • Activate the liftgate on an SUV
  • Lock all doors
  • Unlock all doors

Every car’s code is unique

Every car manufactured has a unique, factory-programmed code. It is stored in permanent memory so it cannot be erased or overwritten. If, however, you want to program a unique code, the keypad also allows you to set aside the factory-programmed sequence and enter your own. Once you enter the new code – the procedure is spelled out in the owner’s manual as well as online – you’re all set. If there comes a time when you need to get into your car’s lock and the customized code isn’t available, you can still use the original code. Just follow the manufacturer’s recommendations to use it.

Common keypad problems

Because of their location on the window frame or on a panel on one of your car’s body surfaces, keypads can suffer from a number of issues including:

  • Dirt contamination
  • Dust
  • Leakage
  • Short circuits
  • Open circuits
  • Sticking pushbuttons

Suffice it to say, each of the problems can cause the keypad to fail. Dirt and dust can disrupt pusbutton closure over time. At first, keypads work well because they of their complete sealing against the weather and contaminants. Over time, though, as keypad protection breaks down, dirt and dust can get into individual keys, preventing their closure. By the same token, water leaks in, around any protective shielding. Shorts and opens, while they have the same result in preventing keypad function, are different electrical failures. Short circuits can result from chafed wires touching screws or body metal while opens are non-working parts of a circuit. A circuit can go open if a part such as a diode fails. Sticking pushbuttons can fail because they stick. They are usually the result of wear.

Repairing a keypad and costs

If keypads are made correctly and properly shielded, they should last for at least 100,000 miles. If you have to replace a keypad, ask your mechanic to find you the best possible replacement for your available budget. Repairing the keypad usually involves replacing the keypad as a unit, not individual keys. It may also involve replacing a wiring loom and connectors. It could also involve swapping out various relays, solenoids and, possibly, the control module itself.


The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Related articles

Symptoms of a Bad or Failing Proportioning/Combination Valve
If your rear brakes are locking up, especially on wet surfaces, you should have a mechanic inspect the proportioning/combination valve.
Symptoms of a Bad or Failing Tailgate Locking Assembly
Common signs include the power lock not working, tailgate lock not latching, and tailgate lock cylinder not turning.
How to Install an Ignition Switch
When When your ignition switch (https://www.yourmechanic.com/parts/ignition-switch) fails, it can cause a number of different issues. You may experience anything from a failure to start, to a stalling problem, to a series of electrical issues. There is never a good time...

Related questions

Running hot with water leaking
Hello, thanks for writing in about your Ford Expedition. From what you've described you may have dual heat on your vehicle and the rear heater core or one of the lines is leaking. It's also possible that your control valve...
Car will crank but won't start - 2006 Ford Taurus
Since you did all this work then you should be able to check the fuel pressure and engine for spark getting to the spark plugs. If you have spark and fuel pressure, then you will need to check the fuel...
Trying to change odometer to kilometers 2005 ford escape
That sounds like a job for the scan tool. It would have to be the factory tool, a generic scanner like the ones they use at the auto parts stores won't do the trick. In many cars the miles/KM setting...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com