Passkey and Engine codes

I recently aquired a 2002 grand prix se, equipped with the passkey 3 system. However the previous owner screwed with it somehow that I just dont know where to start fixing. The security light blinks constantly while the car is running, but the car can be started with a standard, non transponder key. The original key has been obviously tampered with, having the black plastic pulled off revealing the chip inside. I want to fix it so that we can use the keyless entry. Any Ideas on how they may have bypassed the pk3 system?

I am also pulling engine codes (P0420) Catalyst system efficiency below threshold, and (P0440) Evaporative emission control system malfunction. The car starts and runs completely fine, but having any trouble lights on bugs the crap out of me. I have cleared these codes, but they came back, and I have no idea what they mean, or where to start those fixes as well. Any help would be greatly appreciated. Thanks for reading.

Welcome to AF.

No idea on the PK3 issue. The BCM may have some stored VATS codes which can be retrieved with a GM Tech 2 scan tool. Do you have a remote keyfob for keyless entry?

The P0420 DTC is most likely a bad CAT converter. Converter efficiency is less than desirable. How many miles do you have? GM may cover it under an extended converter warranty which affects 2001-2002 models even with the 3100 V6 engine.

The evaporative emissions P0440 DTC see link below:

Click here (http://www.automotiveforums.com/vbulletin/showthread.php?t=622473)

Yea, I got the clicker, but it needs a battery and is missing a button. Dealer wants like $120 just to look at it.

The battery is a coin type 3 volt (CR2032). Which button is missing? You can get a replacement keyfob for under $20. EBay and many on-line RKE stores. Unless the system was really messed up when tampered with or poor band-aid fix the remote keyless entry system using the keyfob should still work even with a Passkey 3 VATS/Immobilizer issue. Technically, these are two separate systems but could be affected through the BCM (body control module).

Thanks a lot for your posts, i put a battery in the remote and the thing worked fine. (The existing buttons anyway)

I would take the covers off the steering column and check that the PK3 reciever wiring is still in tact.