2003 Escalate EXT Rear locks

[tirwin88]

Any idea what this can be now? Where to look?

[Tech II]

Before buying relays, I wanted you to swap them to verify that it was a relay......if the problem moved from one position(lock or unlock) to another, then it was a relay......since it didn't change, it is a circuit problem

So, looking back at the circuit, at rest, both relays ground their respective circuits....when either relay is energized, it goes from grounding the circuit to powering the circuit.....

Since the circuit blows when you hit the "Lock" button, the circuit side(of the lock relay), not the switching output side of the relay, is being grounded/shorted........Diagnosis begins at the I/P fuse block because that is where all three circuits in parallel are joined.....one of those circuits is grounded, and pulling out the fuse block may give a visual of a cut/grounded wire......but those wires go all the way to each of the doors and to the hatch, and if the short is anywhere in those wires, it will cause the fuse to blow........

This is why it only blows in one direction.......since both relays are grounded at rest, there is no problem......when you power one relay, it sends voltage through the wires to the three solenoids, and then the ground at the other relay.....but if that relay circuit is shorted to ground already, there is no problem......however, when we want to go in the opposite direction for the locks, the relays reverse, and the one that was previously powered, is now grounded, and the one that was grounded now provides power....but the first thing it sees before the solenoids is a short, and this blows the fuse.....hope this makes sense....

And like I said, unless a visual inspection shows something obvious, you will have to separate the three circuits at the fuse block to test for a short in each circuit.....this can be done with an ohm meter or a powered test light....

[Tech II]

Thought these diagrams might help.....I colored in red where the short to ground could be....as you can see the lock relay is already in the ground position, so when the unlock relay is energized, it's contact switches position and provides power to the circuit from the right side of the solenoids.....it doesn't matter that the left side of the circuit(in red) is shorted to ground, because that side is suppose to be grounded by the lock relay.....However, when the Lock relay is energized, the lock relay contact moves to power, and the first thing that power sees is a short to ground(red circuit) and blows the fuse....

This is why I say diagnosis begins at the fused block.....you disconnect C4, and with an ohm meter attached to ground, or, a test light attached to BAT, you probe circuits "L" and "K" in the harness.......this will tell you which circuit is shorted.....unfortunately if it is K, it could be either circuit going to either door actuator, and gets a little more involved in testing....

[GMCustomerService]

Originally Posted by tirwin88

Any idea what this can be now? Where to look?

Hi, tirwin88. If you are still having ongoing issues with the fuses/locks, we recommend that you contact your local Cadillac dealership for further assistance. Our team would be happy to provide an additional layer of support and reach out to them on your behalf. Should you like our help, please send a private message so we may further assist.

Cara F.
Cadillac Customer Care