A few days ago, I ran into a problem where my trunk no longer opened when pressing the trunk button. I could hear and see the power struts straining to lift it, but it seemed like the latch itself was stuck shut. Neither the display nor the app would open it either. The only workaround was climbing into the trunk through the folded-down back seats and pulling the emergency release. Once open, the button would activate the power struts to close and open it just fine, but the moment it shut again, it was stuck closed.

Searching online, I only found one or two forum posts describing the same symptom. Those people had replaced the cinch motor, assuming that was the culprit, but that didn’t solve their issue. And they never posted a follow-up on what eventually solved it. I also came across a past recall affecting the trunk wiring harness on earlier Tesla models, where a wire tied to the rear camera would break at the point where the harness bends into the car's body. My rear camera was working fine, and they have since solved the problem with the previous harness, so that didn't seem to apply.

I started by testing the cinch motor myself, since a replacement from Tesla runs about $230. After pulling the latch out (three bolts, accessible once you remove the cover on the underside of the trunk), I applied 12 volts directly to the motor's terminals, and it worked perfectly. Reversing the polarity spun it the other way and let the latch lock. That ruled out the cinch motor as the problem.

Next, I checked whether the cable connecting to the cinch motor was actually sending a 12-15 volt signal when the trunk was commanded to open. This was awkward to test since you have to be inside the trunk while it's closed so the car's computer registers it as closed and tries to unlock the latch. I measured no voltage at all, which meant the fault was somewhere between the computer and the latch, either in the computer itself or in the wiring harness.

To narrow it down, I followed the Tesla Service Manual's procedure for removing the trunk wire harness ([https://service.tesla.com/docs/Model3/ServiceManual/en-us/GUID-6186BA28-196F-496B-8F20-CD5CD6027F1B.html](https://service.tesla.com/docs/Model3/ServiceManual/en-us/GUID-6186BA28-196F-496B-8F20-CD5CD6027F1B.html)) up to step 10. After disconnecting the harness connector, I retested for the 12-15 volt signal coming from the computer side (my wires were red and green) and this time got a solid 15 volts, confirming the computer wasn't at fault.

I then switched my meter to continuity mode and checked both the red and green wires for breaks between the connector and the latch. The red wire showed a break.

At that point I suspected this was the same failure point as the earlier recalls, so I turned the rubber boot at the body of the car inside out. Sure enough, as the photo shows, the red wire was completely severed, and the green wire was close behind it.

This is a serious problem and a genuine fire risk. Tesla really needs to issue a recall on these wire harnesses. I posted this to help out others who may have this issue, but this should be taken care of by Tesla...

2023 Tesla Model 3 - Trunk that does not open is a fire risk...