Is my alarm working? I think maybe not

[irishjag]

When I got the car the fob would not unlock the car. I'm pretty sure this is due to a dodgy micro switch on the remote.
So I got hold of a replacement fob and programmed it to the car and now I can lock and unlock with the fob. I've also got some new switches to repair the fob that came with the car but haven't got round to that yet.

However, when I unlock the car with the key (as I had to 'cause the fob didn't work initially) I understand now that maybe I should've needed to put the key in the ignition to prevent the alarm going off?
Also I should hear bleeps to warn me of this?
Well I can unlock with the key and nothing happens, no bleeps and no alarm if the key isn't placed in the ignition.
Also when the car is locked/unlocked with the key or fob, no beeps and no flashing indicators?
Also when the car is locked no flashing LED anywhere inside to warn that the alarm system is armed which is usual. Where is the LED that should flash?

As I've never had another X350 I'm not exactly sure what should be happening and have just picked up hints from reading posts and the owners manual.
So.. is my alarm not working and if so why and how to get it back up and running?

Any comments/pointers appreciated!

[J44EAG]

Mine doesn`t beep on locking or unlocking, Chris.

It will beep if a door is not properly shut.

Dead centre behind the bottom of the front screen....on the dash top, you should see a red flasher unit which blinks when the car is locked and secured. Do you have that?

Mike

[irishjag]

Hi Mike
Yes I have the LED alright but it never flashes!

[J44EAG]

Broken!

Some diagnosis needed, Chris.

Possibly something to do with the security and locking module, perhaps. Mnnnnn...

Mike

[irishjag]

Plugged in the code reader and got the following;
U1900 can communication bus fault passive anti theft system
U1262 rear module SCP(J1850) comms bus fault

When I looked these up in the X350 electrical workshop manual against U1900 it gives the following as a possible cause;
CAN circuit; open
circuit, short circuit to
B+, short circuit to
ground

So I'm thinking that I've got a connection problem with one of the network cables linking the modules.

For U1262 the X350 electrical workshop manual gives the following as a possible cause;
Drivers door module -
SCP circuit fault Set when
rear electronic module
doesn't send a challenge query

and
SCP network circuit;
open circuit, short
circuit to B+, short
circuit to ground
· SCP network fault
· IC SCP failure

Suggested action;
check driver door to rear
electronic module SCP circuit for
fault

According to the manual the SCP network (standard corporate protocol) links the following modules;· Instrument cluster (IC)
· ICE head unit (HU)
· Rear electronic module (REM)
· Front electronic module (FEM)
· Rear memory module (RMM)
· Navigation module (NAV)
· Steering column lock module (SCLM)
· Electronic park brake module (EPB)
· Driver door control module (DDCM)
· Driver seat control module (DSCM)

So theres a fault somewhere on this network cable, possibly between the DDM and the REM
So i'm going to see if I can check the connectors to these two modules

[J44EAG]

Sometimes just removing the plugs in and out of the module sockets can expose fresh metal on the connections and remove a resistance hot spot. Worth trying to see if things improve, Chris.

Mike

[irishjag]

Anybody know if I need to disconnect Battery ground, or Battery ground and positive before disconnecting the connectors to the cars modules?
If so what needs to be reset after battery disconnection. I have the code for the audio.. Is there anything else?

[J44EAG]

It is quite safe, Chis, to pull plugs on modules without battery disconnection. Just be careful with any +Ve feeds for obvious reasons. Remember many of the circuits are -Ve switched. Also that you will need to have the ignition key turned to Position 1 to power up the car when you are testing.

For battery disconnection, remove the ground -Ve from the battery terminal. If you leave disconnected for just over twenty minutes, this has the effect of clearing down fault codes.....this includes some historical codes which you may not even know were there. Yes, you will need to re-enter the radio code to get the audio going again. The clock will also need re-setting but that is easily done.

Mike