May 18, 2016, 05:53 PM
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Does New BCM have to be Flashed by the Dealer?
Teching In
Joined: Jul 2019
Posts: 12
Likes: 0
I was driving to town and noticed that my door locks wouldn't work by remote or door switch. And I could constantly hear a clicking noise coming from the bcm. I checked to make sure and could feel the bcm clicking. Now the car won't start or anything and the gauges act goofy
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
The door locks problem could be caused by the BCM or the BCM could be clicking because of the locks (stuck input). The starting problem is not the BCM unless the SECURITY light is on (or flashing) in the instrument cluster. The gauges aren't related to the BCM at all.
Check the red/black and orange/black wires in the green 6-pin connector at the BCM. Those are the door lock trigger wires (lock and unliock respectively). It sounds like one or the other may be shorted to ground. They are grounding trigger wires anyway so no fuses would blow but a constant ground would cause the BCM to cycle, creating that clicking noise from the relays.
Check the red/black and orange/black wires in the green 6-pin connector at the BCM. Those are the door lock trigger wires (lock and unliock respectively). It sounds like one or the other may be shorted to ground. They are grounding trigger wires anyway so no fuses would blow but a constant ground would cause the BCM to cycle, creating that clicking noise from the relays.
Teching In
Joined: Jul 2019
Posts: 12
Likes: 0
The security light does come on and flash. Where would those wire ground out to because I've looked thru all the wiring and can't find anything. That's why I was leading towards it being grounded out in the bcm or something
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
The flashing SECURITY light means the VATS in the BCM can't see a resister pellet in the ignition key (i.e. open circuit). It would be on solid if it could see a resistance but it didn't match the programmed value. There are many ways the circuit could be open... a break in the wires, the orange connector under the steering column unplugged, bad contacts inside the ignition cylinder, or a damaged key. Depending on the cause, you can either fix it or just do a VATS bypass.
The door lock inputs ground at G200 - the ground stud behind the left kick panel. But the problem here would not be a bad ground but rather too much ground... one of the wires having damaged insulation and grounding out against something metal under the dash or inside the door. It's easy to test - unplug the green plug and check continuity to ground on those two wires. You should only see ground when the lock switches are engaged, otherwise there should be no continuity.
The door lock inputs ground at G200 - the ground stud behind the left kick panel. But the problem here would not be a bad ground but rather too much ground... one of the wires having damaged insulation and grounding out against something metal under the dash or inside the door. It's easy to test - unplug the green plug and check continuity to ground on those two wires. You should only see ground when the lock switches are engaged, otherwise there should be no continuity.
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Then I would check that your bypass resistors haven't come loose or disconnected. That's the only explanation for the flashing light other than a broken wire somewhere between the bypass and the BCM.
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Verdad Gallardo Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
It's not an orange wire... it's two white wires in an orange sheath under the steering column.
You're lucky. When the BCM finds a VATS resistor issue while the engine is already running, it considers it a system fault rather than a theft attempt and will allow the car to be started despite the fault. If it discovers the resistance mismatch while starting the car, it will prevent the car from starting until the correct resistance is seen. That's why you've been able to start the car even with the obvious error indicated by the security light. Still, it's not something to be ignored - the system has been known to reset when the battery is disconnected (for battery replacement or other electrical work) and treat future resistor mismatches as theft attempts and block starting the car.
You're lucky. When the BCM finds a VATS resistor issue while the engine is already running, it considers it a system fault rather than a theft attempt and will allow the car to be started despite the fault. If it discovers the resistance mismatch while starting the car, it will prevent the car from starting until the correct resistance is seen. That's why you've been able to start the car even with the obvious error indicated by the security light. Still, it's not something to be ignored - the system has been known to reset when the battery is disconnected (for battery replacement or other electrical work) and treat future resistor mismatches as theft attempts and block starting the car.
Staging Lane
Joined: Dec 2017
Posts: 52
Likes: 0
From: Virginia
And how would it detect a mismatched resistor when the resistors in my Original keys are the original? If it accepts them now. it should accept them always? I think there is a loose wire or something else that has caused the Security light to stay on for 4-5 years now.
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Sorry... I don't understand the question. You get to the wires by climbing under the dash on the driver's side and looking up at the steering column to see a small harness with orange insulation (sheath) with two white wires in it. There is also an inline connector attached to those two wires which you can unplug and use as a point of testing or as a place to install bypass resistors.
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Often the change in resistance is caused by grime on the key pellet or the contacts inside the ignition cylinder. Also, corrosion on those contacts in the cylinder can cause an inaccurate resistance reading. Or the wires to the contacts in the cylinder could be damaged.
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
No, the wires will be visible without removing any dash or trim pieces. Nothing untoward will happen if you unplug the connector. The two wires are simply part of a closed loop between the BCM and the contacts in the ignition cylinder to measure the key pellet resistance when the key is inserted.
Joined: Nov 2003
Posts: 11,331
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
You may have to remove the knee panel although it was not necessary on my car. The knee panel is the plastic panel under the steering column.