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View Full Version : Wireless door lock can only lock

dj92
09-30-2014, 04:10 AM
Hi,
I'm encountering a quite strange error:
By fob, I can only lock the doors (this works always), unlocking is impossible most of the time.
What I've done up to now:
-re-paired fob and receiver
-disconnected both the battery of the car and the fob for some time
-checked the lithium battery voltage (seems ok, 3V)

The car's battery seems ok to me as the headlights dim only subtle when cranking.

The fob's led lights up for both keys.
I have used the diagnostic mode of the door lock (interior light blinking) and found out that the opening command isn't received at all.

The lock system itself seems innocent to me as I have no problems using the key at the door and the buttons inside.

I initially guessed there would be an interrupted line from the receiver to the body ECU, but iirc the information is transmitted serially.

I'm not sure whether I should replace the receiver or the fob.
The first one can be had for about 40$, while the latter one is almost impossible to get.
CTScott
09-30-2014, 08:17 AM
Try cleaning the PCB of the fob first. It may be that the switch contacts are dirty and the unlock one does not get properly activated.
dj92
09-30-2014, 12:15 PM
Damn, looks like I fixed it :biggrin:
I took out the PCB and went to my car, pressing the battery holder onto the PCB and hooray it worked again.
As I have some skills on that subject, I soldered the contacts onto the PCB, now it works again like a charm :)
dj92
10-01-2014, 01:18 PM
I added a 10µF ceramic capacitor to the existing (small) ones.
This considerably increased the fob's range (before 3m, afterwards 10m).
I measured the battery's ESR which was about 17 ohms, which might be a reason for the low range before.
No, I don't want to buy a new battery yet ;)
jcboy
10-01-2014, 03:27 PM
I added a 10µF ceramic capacitor to the existing (small) ones.
This considerably increased the fob's range (before 3m, afterwards 10m).
I measured the battery's ESR which was about 17 ohms, which might be a reason for the low range before.
No, I don't want to buy a new battery yet ;)

great, but that can be a catch 22. a farther range could mean a farther possibility of accidentally pressing the unlock button. our cars re-arm only after 30sec.