DIC "security system problem"

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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, DIC "security system problem" in Past Cadillac Vehicle Discussion; My '96 deVille always displays the messages: "security problem" followed by: "car may not restart" every time it's started. (car ...
  1. #1
    cormorant is offline Cadillac Owners Member
    Automobile(s): '96 Sedan DeVille
    Join Date
    Oct 2013

    DIC "security system problem"

    My '96 deVille always displays the messages: "security problem" followed by: "car may not restart" every time it's started. (car always restarts). I have both original keys with the little chip in the
    ignition one, so they're not hardware-store duplicates, but the car seems unable to read them any more--if that's what's causing the code. (This has been going on for over a year). Any suggestions on how to get rid of these messages? I'm not much interested in doing a new ignition switch or other pricey resolution, if possible. Thanks for the always helpful advice!

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  3. #2
    rodnok01's Avatar
    rodnok01 is offline Cadillac Owners Master
    Automobile(s): 98 DeVille, 97 DeVille d'Elegance
    Join Date
    Feb 2012
    Have you checked codes? Could be VATS issue, if so for a few bucks and an hr you could bypass it.

  4. #3
    cormorant is offline Cadillac Owners Member
    Automobile(s): '96 Sedan DeVille
    Join Date
    Oct 2013
    Thread Starter

    Re: DIC "security system problem"

    That sounds good to me and I can check the DIC codes, but pardon my ignorance--what's VATS?

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  6. #4
    Cadillacman916 is offline Cadillac Owners Member
    Automobile(s): 07dts perf. 04 dts,06 dts limo,11 dts, 13 escalade, 13 xts
    Join Date
    Jan 2013
    Sacramento, ca

    Re: DIC "security system problem"

    I am too lazy to explain myself but I Found this explanation of vats here: @ http://www.fastfieros.com/tech/gm_vats_passkey.htm
    Its essentially the same system.

    Understanding GM VATS (PassKey)

    This system seems to cause much confusion, stress, and misery. Hopefully, this will help elevate

    some of that. VATS stands for Vehicle Anti-Theft System. It is commonly referred to as PassKey.

    Later versions include PassKeyII, PassKeyIII and PassLock (which uses no resistor "pellet"). GM

    first introduced VATS in 1985 on the Chevrolet Corvette, and after proving successful, was later

    introduced in other models in later years. Lets break it down even further:

    Operation: Operation is fairly simple, but lets discuss what all makes up the PassKey system.

    The most obvious part is the key. The ignition key as a little "chip" in it. This is a resistor

    "pellet". There are 15 possible resistances, therefore 15 different types of keys each with a

    different resistance. This reduces the likelihood of a potential thief from having the correct

    resistance resistor on hand. Then you have to have a special lock cylinder to "read" the key. I

    use the term "read" loosely, because it does anything but read the key. I will explain more later.

    Next is the VATS module. It does most of the security work. It is the "brains" of the system.

    The module is what actually "reads" the resistance, but has to do it via the contacts in the lock

    cylinder and the related wiring. Think of the module as a Multimeter, and the wires and contacts

    the Multimeter Leads. The module reads the resistance and determines if the resistance is the

    correct value. The module will go into several modes, depending on what the module sees. There

    is "Tamper" "Normal" and "Fail Enable".

    Normal: Normal is when the correct resistance is seen during cranking and the module will ground

    the Start enable relay, and send a "Fuel Enable" signal to the ECM. This basically "turns on" the

    injectors. If the Fuel Enable signal is lost or not sent, the injectors will never pulse. The signal is a

    unique "Pulse Width Modulated" signal, which is a series of rapidly switched "on" and "off"

    voltages that would be near impossible to duplicate. Once the relay is grounded, voltage is allowed

    to the "S" terminal of the starter, and the ECM is told to pulse the injectors and the car starts.

    Tamper: This mode happens when the vehicle is cranked, and the resistance value as seen by the

    module is not the same as the value stored in the module. When this happens, the module shuts

    down for 4 minutes. Even if the correct resistance is then seen, the car will not start for the 4

    minute "time-out". The security light will also illuminate for the 4 minutes. The Start Enable

    Relay will not energize and the Fuel Enable signal will not be sent. HINT: if the key pellet is dirty,

    it will put the module in the "Tamper" mode. If your car fails to crank/start and the security light

    comes on, try cleaning the pellet, wait 4 minutes, and try again.

    Fail Enable: This mode is to help keep the motorist with the right key from being stranded. If a

    failure happens to the PassKey system AFTER a valid start, this mode is initiated. It allows the

    vehicle to be restarted, even with a failure present. The security light will remain illuminated to let

    you know a failure is present. However, this also means that the car can be started w/o a key, and

    is vulnerable to potential thieves.

    Lets take a look at the basic setup.


    If your car doesn't want to crank and the security light comes on, here are a few things that may

    hopefully get you back on the road:

    First, make sure the pellet is clean. A dirty pellet will give a higher resistance than what the VATS

    module expects to see, and assumes it is the wrong key.

    Check all of your fuses. If a fuse is blown or missing, it can cause a security problem.

    Obtain a multimeter and measure the resistance of the key. Then remove the hush panel on the drives

    side of the dash and find the wires that go to the lock cylinder (usually two thin white wires, sometimes

    with orange insulation around both). Now measure the resistance at the two wires with the key in the

    ignition. If it doesn't come within a few Ohms of the original key resistance, the lock cylinder is bad.

    If the resistance comes up OK, measure it again, this time while moving the key from "Off" to "crank"

    several times. Any fluctuation in resistance means a bad lock cylinder. This is the most common cause

    of failure. The wire are anchored to the stationary steering column, but attached to a rotating lock

    cylinder and over time, the wire breaks inside the insulation and usually becomes "open" in the crank

    position. This is read by the module as an incorrect resistance.

  7. #5
    cormorant is offline Cadillac Owners Member
    Automobile(s): '96 Sedan DeVille
    Join Date
    Oct 2013
    Thread Starter

    Re: DIC "security system problem"

    Thanks for all the detailed information. I'll look into the resistance angle. When I bought the car, the seller showed me how the "Theft System Problem" and "Car May Not Restart" messages always come up, but the car always starts. He claimed someone before him had 'disabled' the security system in the steering column, but was pretty vague about it. Tapping the Info button cancels the messages until the next start-up. No security light ever comes on and the car has never gone dead for several minutes. I have tried cleaning the key's button, with no effect. I was hoping there was some way to just kill the whole system and not have to deal with the messages every time I start it--especially if I loan the car to anyone, as they get all worried.

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