Questioni have a question about the theft system. this lady locked her door with her key and the alarm went off, but now seems to be stuck in anti theft mode. car will start but dies seconds later. the dealership suggested a new computer, so computer has been replaced. ordered brand new but still does the same thing. the dealership tried to hook their computer up to it but it kicks them out and wont let them get any info from it, everyones at wits end trying to figure this car out..any suggestions?
AnswerHi Christina,
I would not pay the dealer for the new computer and instead have them put the old computer back in the vehicle. That is an example of 'throwing parts' at a problem instead of analyzing it.
To begin, verify that fuses 4 and 12 in the fuse box in the engine compartment are good, and that fuses 5 and 7 in the fuse of the dash are good before doing anything. Those are the fuses in the theft system. Also, check fuses 8 and 15 at both locations as well as fuses 9 and 11 in the dash box as all those fuses are involved with the body computer's functions.
There are several possibilities for what to try:
First I would verify that neither door key lock will disarm the theft system. Both doors are connected to the body computer but the wire from the driver door may be disconnected or shorter to ground. So try to lock, then unlock, the passenger door using the door key. See if that has disarmed the system so it will then start and run. If so, then either the driver door lock switch can be repaired OR if the lady will be very careful to never use the door key, the power door locks, or a remote key fob to secure the vehicle in the future then she will never reset the alarm again. The way to secure the vehicle is to only use the mechanical push button lock tabs on the inside of the doors when closing the vehicle and it will be just like the good old days before anti-theft systems.
Second, the doors may be too loosely closed because the striker in the door frame which mates with the latch in the door may be too far outboard, which then gives the computer the false information that the door is 'open'. There are 2 screws on each door striker which can be loosened and allow the striker to be moved in-board a few millimeters so that the door is pressed tightly against the frame when it is closed.
Third, the electrical function of each door key lock can be measured at the pin on the plug for the body computer. That would verify both the wire connection for each door as well as the electrical function of the door lock (there are 2 different values of electrical resistance (940 ohms when the key is moved to the 'lock' position, 470 ohms when the key is moved to the 'unlock' position). The driver lock wire is on pin #20 and for the passenger door is on pin 19. This would have to be measured with everything 'off' and the measurement made between the cold side of fuse #5 in the fuse box at the left end of the dash WITH that fuse REMOVED.
Lastly, one can take a 470 ohm resistor from an electronics store and use it to jump briefly (one touch) between the light green/orange wire on pin 19 of the black 20-pin plug of the body computer and any 12 volt supply point nearby to that pin. That is basically the way the door lock signals the body computer to disarm the system and allow the engine to start and run.
Please let me know how this works out. The shop should be able to do these steps quickly as I assume that the vehicle is stuck there.
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Thanks,
Roland
