Hi. I've had this issue all these years I've had this car. This summer this not so funny issue has gone worse. Keyfob working range seems to vary a lot. But that is ok. Couple days ago I soldered buttons to the fob to be sure it is not the bad contacst in the fob pcb and resolderd all of the components exlcuding stuff under the "can". I'm pretty sure fob works now and or has been working since last year I glued new conductive rubber pads to the buttons.

Today I went to the car to measure how trunk lock sense switch is working. It does work great. BUT. What I've found was very weird sense voltage to the microswitch. It was floating and nothing even close to every other car i've have been measuring during my mechanic years. What these voltages should be are clear voltage difference from the 0V and when switch ties voltage down it is 0 and nothing else. And if switch floats so the voltage is not steady up or steady down it can and will cause nasty problems.

I measured very floaty 1.5 - 2.0V paraller to to the switch. It did not make any difference was the switch connected to the circuit or not (lid was open and lock closed). So the switch is not floating at the moment at least. To rule out hinge wiring issue I measured at the security and loking module end of the red-white wire and got same voltages range. Button and microswitch earths are ok.

Next to be kinda more sure I measured voltage in same manner from the trunk release switch. Almost same kind voltage range from there.

So, after this long explaining the question is does those voltages are okay ? Usually those kind of voltages across car makers are like 5-7V Not floaing 1.7V. Last year car complained about trunk lid to be open during driving. But it cleared out as fast as it came on. This summer no complain. If voltages aren't corrent no wonder it is complaining. It is then either repair the security & locking module or try to locate one possibly more working one.

 

Just looked in the box and carefully read wiring diagram. Diagram states :
TRUNK SECURITY SWITCH STATUS ACTIVE = GROUND (INTRUSION) INACTIVE = B+ (SECURE)
TRUNK RELEASE REQUEST ACTIVE = GROUND (MOMENTARY) INACTIVE = B+
Pretty clear that I have faulty module. Unless hinge wiring loom is badly hacked.

Pin BT2-5 (lock switch) goes straight to the transistor at the pcb. Transistor checks out fine. I just cant turn on the module at the desk. So I can't measure why there is no battery voltage pull-up going on. I have both grounds and one power hooked up and nothing. It may wake up via bus.

 

Yep. Measured voltages at the pcb when connected to the car. Lockswitch voltage was at battery voltage as it should and button was 1.7 as always. Figured out that this could be classic cold solder joint case. And it is! By gently twisting the pcb from certain place while measuring voltages from the button and switch I could get voltages anywhere between battery and 1.5V,

So resolder eeeevery joint is next thing to do. I may not dare to do it by my self. But we will see. I might be on to something here ? Coz this is not the first faulty SLM in the planet.