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Key Diagnostics and Programming

Key and security system diagnostics are not that much different than driveability diagnostics.

Andrew Markel is the director of content for Babcox Media.

It happened to me, I left my car keys in my pants and threw them in the washing machine. Thirty minutes later, I heard a knocking noise coming from the dryer. The key was toast.

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With more vehicles using remote fobs and proximity keys with sophisticated electronics inside, replacing a damaged key due to an accident like mine will become more common.

The key is only one small component of the total immobilizer or security system/strategy. With some vehicles, six different modules in the car might use the code from the key. If the vehicle has a new module, relearning the keys and key programming tools might be required. 

If you think that programming keys is just connecting to the OBDII port and putting a blank key on a programming pad, this is the wrong way to approach this service and tool costs. Most of the time, a key tool will be required for diagnostics. 

What is Going On?

Immobilizers and keyless entry have done great things for vehicle owners. New vehicles are tougher to steal thanks to more advanced immobilizer systems. These systems have been more useful for discouraging thieves by making the most expensive vehicle parts unusable by requiring security information. Keyless entry has made it possible to enter a car without pressing a button or start a car from inside the house.

The implication for technicians is that no-start, no-crank and module diagnostics have a possible fault with the security and keys.


Key and security system diagnostics are not that much different than driveability diagnostics. The biggest difference is that access to the vehicle through the OBDII port might be limited because of the lack of a valid key. This can limit communication with some modules.

This is where the differences between locksmith tools for coding keys and diagnostic tools that can code keys become apparent. In the past, key coding tools resembled 1980s hand-held computer games. Many of the tools have limited coverage and capabilities to perform diagnostics.


With the remote fobs and proximity keys on most vehicles, being able to diagnose and service keys is now an essential skill. 

Various situations might require key programming capabilities, including being able to diagnose and program keys as part of no-start diagnostics, needing to reprogram a key or fob to the vehicle if a module was replaced or providing a customer with an extra key (or if all of the original keys were lost).

You might think that key programming is a job for a locksmith or specialist, but the market has changed. While brick-and-mortar locksmiths and dealership parts departments can cut key blanks, it is up to the technician to make them work with the vehicle. In the case of some proximity keys, there is no key to cut — it is all up to the tech.

Reflashing and Reprogramming

Data can go both ways when it comes to some key programming tools. Information from a key can be programmed into a module, or information from an existing model can be programmed onto a key. This tool function can save you if a module has been replaced or reflashed, and the key information is lost. It is also helpful if you are in a situation where all the keys have been lost.

For situations like this, you have several options. Some key programming tools and vehicles will allow you to clone key transponders in the vehicle’s memory. The key programming tool communicates with the car to find the information about the existing keys and then burn that code to a new transponder using a specialized attachment for the key.


On some vehicles, the situation may call for reflashing completely new transponder codes to a module. For some cars, this can be performed through a J2534 interface. Other cases may require the module or EEPROM chip to be removed for reprogramming. Specialized key programming tools let you do it at your shop.

The key for modern vehicles is more than a key. Modern keys and fobs can start a car remotely, open a rear hatch with a swipe of a foot, and make sure the vehicle is secure against physical and virtual attacks. If you are already servicing these vehicles, you can’t avoid key programming.

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