I've got a problem with my 2001 Volvo S60 ignition key. One key will start the car no problem. Most recently, however, the other key will turn and the engine just grinds but won't start. Put the other key in, and the engine starts! Volvo whats $149 to check my system out before they will acknowledge that it's the key. How do I do this more cheaply?
If you are looking for a method by which you can diagnose the problem to confirm your suspicions that one of your keys has failed I can suggest the following.
In close proximity to the ignition barrel, literally around the outer radius, is an RFID reader. When you place the key in the ignition, this energies and attempts to rear the transponder code from the ignition key.
Embedded within the plastic part of the key is an RFID chip which responds with a unique code. If the car either does not receive this code or receives a code which it does not recognize, it will either not start the engine or the engine will start and them immediately shut down.
To confirm that this is happening you could hold the key which you know does work against the transponder ring whilst trying to start the car with the key which does not work. If the car starts, you know that one of two things has happened. Either;
The transponder in the bad key has failed
The transponder code is no longer recognized by the car which it is attempting to start
In either circumstance, what you do if you prove this is entirely up to you. From what I've read online, Volvo keys can only be added by a main dealer as you need to purchase a new (not used) key. New Volvo keys include a slip of paper which features a security code which the main dealer needs to give the car in order for the car to start accepting the new transponder code.
This would be one option but obviously it would be costly and if the car isn't work much, is probably not economically viable.
Another option would be to only use the know good key with the car. Place the other key somewhere safe and accept that all it will let you do is unlock the car should the known good key become locked in the car.
One final option, which I've seen done a few times, is to extract the transponder chip from the key and secure it to the transponder ring. This will therefore mean both keys will start the car but will effectively disable to engine immobilization built into the car. If the car isn't worth much and isn't likely to be stolen but you do need two working keys, perhaps this would be a good option.
Just make sure you don't loose the known good transponder once it's been extracted from the key.
A slight alternative to this, which again, I've seen. Keep the transponder hidden somewhere securely in the car and hold it against the transponder ring only to start the car. This brings back an element of the security but still would allow both keys to be used.