Dear Ask a Mechanic,
A few weeks ago, both the remote button and the switch for the trunk release in my 2013 Cadillac CTS stopped working. I checked the fuse, which is in the panel, and it was fine. When I found out that the release was built into the trunk’s latch I replaced it with a brand-new part, but it still doesn’t work. The only way that I can open my trunk right now is by pulling the emergency release handle. What am I missing? – Trunk troubles
Looking at the wiring diagram for your vehicle, there are several components involved in your Cadillac’s trunk release system, including the remote control door lock receiver, the body control module and a relay that’s located in the same rear fuse block as the one you checked. (Hopefully you probed the fuse with a test light to verify power at both pins. I’ve been fooled by fuses that appeared okay but weren’t.)
One quick check that you can do is to see if pressing the trunk release switch or the button on the fob triggers a reaction from the relay. It should make a clicking sound in response and I’d expect that you should be able to hear it inside the trunk area.
If there’s no reaction, then the control side of the circuit becomes suspect. Since modules and data networks are involved, you’re probably going to have to take it to a repair facility that has a GM-compatible scan tool to properly diagnose it.
If the relay does click, then you would need to determine why the latch is still failing to operate. When the relay is triggered, battery voltage is fed directly to the actuator, and, with a helper, you can check for this power at the latch’s connector. Bear in mind that a complete circuit is required, so there must also be a ground wire present for the mechanism to function properly.
Based on more than one encounter I have had with faulty trunk latches (and because you have replaced the old latch with a new one), I predict there is an issue with the power, ground or both wires at the latch. Broken wiring between the trunk lid and the body of a vehicle is common, as the wiring is flexed every time the trunk is opened. And, like the tab on a pop can, eventually fatigue occurs and the wires break, sometimes without splitting its insulated covering. (Fatigue failures occur regularly in door and tailgate wiring, too.)
Repairing the wires might be the solution, and chances are that other wires in the bundle are also broken, so inspect them all during any repair.
Ask a Mechanic is written by Brian Early, a Red Seal-certified automotive technician. You can send your questions to email@example.com. These answers are for informational purposes only. Please consult a certified mechanic before having any work done to your vehicle.
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