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Good day, I'm a relatively new member and have read so much I can't read anymore. PROBLEM... when pressing the trunk release, the actuator doesn't activate. Found 4 broken wires in the conduit that bends when the trunk opens and repaired them even though no voltage was present while having my son press the trunk release. ACTION- checked trunk on/off switch in the glovebox and no power going to it either. ACTION- Check for power at the switch near the left leg also and no 12 volts are present. ACTION- check all fuses (not relays) in the cab by left foot as well as fuses under the hood near the battery and all is good. I'm helping my son out by fixing it for him to save money and I'm pretty good when it comes to electrical troubleshooting and troubleshooting in general but am a little stumped on this one? No other issues present that would indicate a bad BCM either. Any thoughts???? Please help so I can solve the issue!! Yes the battery is fine with full 12 volts and car starts and runs fine. Just the trunk releae issue and center light on trunk hood getting zero volts. Regards, Darin
The signals for the trunk actuator and trunk light do indeed pass through the BCM as you can see by the two attached pics below. Finding and repairing the broken wires leading to the trunk was the correct first move. Does the 3rd brake lamp work? If not, test the black wire at the actuator and at the lamp assembly to be sure it shows continuity to ground. I believe both these operations and the center brake lamp share that ground. No ground could account for the actuator and lamp operations failing, however, I think you should have seen +12 appear at the actuator's green wire when operating the dash switch (try it with the glove box switch in either position). There are no separate fuses or relays involved in these two circuits, the logic and power switching is done by the BCM. But I think if the BCM was the problem you would be experiencing have many other unrelated issues so keep looking at the wiring side before worrying about that. Please doublecheck your repair of the 4 wires leading into the trunk lid.
EXCELLENT REPLY AND SUPER APPRECIATE THAT! Thank you Skyline. The center brake lamp is indeed not working either so that may be an issue also however with my meter grounded on the trunk body latch, I still do not see 12 volts from either the center light or the trunk actuator power. When I trace back to the glove box switch and trunk switch in the car, there's ZERO voltage there either. I have high-quality meters that I use daily and know there's no voltage. I am going to trace the wires further as per your recommendations. Thanks again!
Strange about the lack of +12 anywhere. Keep digging. But because the center brake lamp is also not working and they all share that black ground wire, use your meter in continuity or impedance mode to be sure the black wire is grounded to the car's chassis.
The switch in the trunk and the switch on the dash will NOT have power, it's a GROUND signal to the BCM.
When you hit the switch you complete the circuit to ground, when the BCM sees ground it will trigger the actuator, the actuator is the only thing that will have power.
Try backstabbing the BCM harness with a paperclip on pin 30 pink wire, then use a bit of wire and touch that pin to chassis ground. The trunk actuator should operate at that point and you will have 1 second of 12vdc on pin 68 green/white stripe.
When testing from the dash switch in the driver seat you should have continuity to ground on one half of the switch. When you hit the switch it should have continuity through the switch, with the glove box switch ON you should have continuity from the driver seat dash switch back to pin 30 pink wire on the BCM.
So from your post, it makes sense that the only time 12 volts complete the circuit to the trunk actuator is when the trunk switch on the interior of the car is pressed? Which grounds out the BCM and sends 12 volts to the actuator correct?
So from your post, it makes sense that the only time 12 volts complete the circuit to the trunk actuator is when the trunk switch on the interior of the car is pressed? Which grounds out the BCM and sends 12 volts to the actuator correct?
Correct. Grounding pin-30 of the BCM will send one-second of +12 out pin-68. And grounding pin-57 will send +12 to the trunk lamp out of pin-64 until that ground is removed - although there may be a max timer on that circuit as a battery saver.
