The last 2 times I have started my car, when it has sat for a while and is cold, the security light has stayed on, and I have to turn the engine off and re start it, and then the light goes off. Does anyone have any ideas on what may be causing this? I have no clue!

Thanks!

Rob

 

Just to clarify the condition, you'll need to specify what the light is doing prior to starting the car. This is the normal operation:

1. Unlock the door and open the door - Security Light Flashes.
2. Close the door, put key in ignition and turn to ON - Security light goes OFF when key turned to ON.
3. Start the engine - The Security Light will go ON for several seconds then turn OFF.

If the light is only staying ON at step 2 then the service manual says to check the following circuits for intermittent issues:

• Driver and passenger doors ajar switches.
• Trunk/Hatch ajar switches.
• Power Door Lock switches.
• Intermittent communication problem between BCM, IPC (ignition switch), RDCM/LDCM (Right and Left Door control modules) and PCM.

If the light is not going OFF in step 2, then the issue is likely in the BCM or other no-communication issue.

Since it's intermittent, it sounds like one of the circuits listed that could be giving you a problem including the grounds for those circuits. Check those out and see if it improves.

 

I will check today! I appreciate the help!

Thanks!

Rob

 

My light goes off when the key is in the on position, but after starting the car when the light comes on for a few seconds and is supposed to go off, it sometimes stays on. I turn off and re start and the light reacts normally.

Thanks again!

 

Since the light goes off when the key is in the ON position, and the car starts (starter not disabled) it means that the BCM is satisfied with all the input parameters, especially the Pass-Key pellet, to disable the theft deterrent system.

Now why the light comes back on after the car is started is strange - but it's controlled by the BCM and could be caused by it seeing one of the input signals change due to an intermittent connection. My guess would be the contact switch inside the ignition key cylinder may be starting to have an intermittent problem that happens when the key is returned from START to ON and causes the BCM to see a wrong signal (like a KEY OUT signal).

Check the DIC codes to see if there's anything stored that could point to one of these problems.

Hope it works out.

 

I did'nt know you could check DIC codes even if none come up for a problem. How do I go about this procedure?

 

The C5 has two antitheft systems :
One is the Content Antitheft, the second is the Vehicle Antitheft. The security light stays ON after the car is started if there is a problem with the Vehicle Anti -Theft system. The security light tells you the status of the Content AntiTheft system (Horn alarm) when the key is OFF. If the Key is ON, or engine running, the Secuity light is the status of the Vehicle AntiTheft system (VATS, Starter cut-toff, fuel cut-off). The light will stay on if there is a fail-safe fault with the VATS or Fuel cut-off. Based on the VATs system of the BCM, that enables the starter and sends a coded data-word to the PCM to enable fuel. IF the BCM first sees the correct key resistor value when the car is started, but then sees the wrong resistor value when the car is running, (open or short VATS wiring to the lock cylinder), this sets a fail-safe mode, which illuminates the security light. This fail safe mode basically disables the VATs so you can still restart and drive the car, but the problem should be fixed. There should be a fault code for this set in the BCM.

 

Could this problem be caused by a dirty resistor in the key?

Anyway, this problem has been very seldom. Most of the time all seems fine, however, I do want to find the reason and correct it if I can.

Much thanks!

Rob

 

Yes, dirt key contacts or dirty ignition lock contacts (or worn/bent contacts) can cause this. Also the wires and connectors from the lock contacts to the BCM can be intermitent.

 

I cleaned my key (resistor), although it looked pretty OK. Anyway I have'nt had a problem since. That may have done the trick and I thank you guys for the help!

 

Since allmee seems to have his issue fixed, i'd like to ask about the security light.

Sometimes with the car running, i'll hop out to get the mail when leaving or something. About half the time, the security light will come on and stay on after i get back in. The car runs fine the rest of the trip, and the light is off the next time I drive the car.

I was just wondering if there was a procedure I need to follow for a situation like this, or if this was indicitive of a problem?

Thanks!

-Rich

 

My light stayed on while driving home today.....I know I "drive it like I stole it" but this is ridiculous!!

 

Yes clean the key with some rubbing alcohol. This is the first step then it the problem continues there is something wrong other places.

 

FWIW, I had the security light come on while driving a couple of weeks ago. I am guessing it might be from going around foothill twisties like a bat out of, well, somewhere, but going rather fast, and having about a pound of other keys hanging off the key ring while doing that.
Maybe the weight pulling on the ignition key helped cause the code to set. Hasn't happened since.

 

Weighted keys are not good for any ignition. It wears on the ignition parts tumblers and such.

 

Where are the ignition lock contacts and the sensors that detect the resistance on the key located?

I recently replaced the ignition switch and looked for other contacts to clean while I had everything opened up, but didn't see any other contacts or sensors to clean.