Hi at all, one my P38 fellows has a strange problem. When he inserts the key in he ignition barrel the alarm sets of ... horn/indicator. Fob unlocks and locks without any issues. Anyone ever had this phenomena? Hints, where to start? Car is not with me at the moment ...
thanks
Kurt

When he unlocks with the fob, does it turn off the red alarm LED on top of the dash or does it continue flashing?

I´ve asked my friend. Everything works, as it should. Car unlocks with the fob, LED is off when unlocked and blinks when car is closed. Starts and drives normal, but with alarm. He has disconnected the horn etc.. As soon as he inserts the key the alarm gets off. Seems like the microswitch or the receiver in the ignition barrel. It is an early Thor from 99 V8.

An odd one. If the microswitch in the lock barrel has stuck, normally the dash will tell you the key is in even when it isn't when the door is opened. It will also cause a mislock beep when locking. I suppose it is possible that it has failed open circuit so it doesn't detect the key in the ignition and that could set the alarm off when the ignition is switched on, but not as soon as the key is put in the ignition (as it wouldn't know the key has been put in the ignition). The coil around the lock barrel is there to cause the fob to transmit the unlock code as soon as the key is put in the ignition so it resets the immobiliser if passive immobilisation is still enabled. As far as I know it is only the immobiliser that comes on with passive and not the alarm too. Also, if passive is still enabled and the coil has failed so the unlock code isn't being sent, you would get the Engine Disabled message on the dash.

Yes, it is very strange ... I guess, I have to check it myself with the car and dig deeper into the alarm system and its connection to ignition barrel. Will take a while until the car gets to me, it is in France at the moment ... sadly the fellow doesn't have any diagnostic equipment.

update ... car was at a dealer and they disconnected the receiver coil in the ignition barrel. That helped for two days until the alarm went off while driving on the highway.
I have now the suspicion that either the fuse box, the earth points or finally the BECM may cause the erratic behaviour, as the fuel filler refused to open for some reasons (it finally opened up and I told the fellow about the manual override in the late models ;-) )
I´ll keep this updated, as soon as we know more. Very strange ...

I know the BECM has a lot of connectors, but unplugging and reconnecting electronic connectors (battery disconnected) can sometimes solve gremlins. I recently solved a window and odometer problem on my D2 by reconnecting the BCU. I’m an aircraft mechanic and this often works on airplanes as well.

Hi Harv, we´ll try this tipp. THX!

I'd be more inclined to look at the fusebox than the BeCM. BeCM does what it is told by other things so unless it is swimming in water and getting false grounds, it is unlikely to be the cause. A failing fusebox isn't uncommon and will cause all sorts of random intermittent faults.

Richard ... i came to the same conclusion, Thanks a lot. There where other errors reported, like alarm going off when the lights get switched on etc. A new fuse box is on its way, will update once it is installed.

From your last post, I would lean more toward a bad earth point.
When you turn something on, (especially a high current drawing device like lights) and something else acts up on a P-38,
It is usually an corroded or loose ground.
New fuse box will certainly not hurt, but run through the earth points as well.

i Bolt, exactly my other recommendation, too. Thank You very much for the suggestion!

The saga continues ... new/used fuse box did not change the off behaviour. Funny finding, opening the fuel flap will trigger the alarm, too. Even if the car is unlocked. What can trigger the alarm if the car is unlocked? Why? Why is the car "armed"?

This made me curious so I've just gone through the BeCM SID to see if I can see what arms the alarm. There doesn't appear to be a specific line that gives an output when the alarm is armed other than the feed to the LED on top of the dash. There's inputs from the ultrasonic sensor and from the door latches and outputs to the sounder but nothing that appears to be alarm specific. I suspect it is a case that if the ignition is off, the engine isn't running and the doors are locked, that enables the alarm system. This would suggest that, for some obscure reason, the BeCM is triggering the alarm sounder so it could be a BeCM fault.....

It´s not only the alarm horn, it is the main beam, indicator etc. the full program. Really strange, we think of swapping the BECM.

That's a setting in the BeCM as to what happens if the alarm is triggered, hazards, main beam, horn, whatever combination you want. However, looking at the Nanocom documentation, under BeCM - Settings - Alarm, it says this:

· Alarm: The alarm can be either enabled or disabled if required. Disabling the alarm
prevents the alarm from arming and stops all audible and visual activity whenever the
vehicle is locked or unlocked. It does not affect the immobilization.

So if it can be disabled, that should cure the problem.

Hi Richard, Good advice as always. I maybe made the mistake of never ask him, if he played with these options, as he got a Nanocom from a friend in Germany. So I assumed they have played with the Alarm Settings.But will re-check!
THX

The saga continues …my friends got a Nanocom from another fellow. We could not deactivate the alarm with the Nano. Neither the individual alarm functions (indicator, main beam etc.). The alarm sets of immediately when the ignition is switched on. As far as I know the transponder ring in the barrel has been cut and this solved miracously the alarm problem for a while, which has returned during driving and did not disappear since then.

What could trigger the alarm when ignition power supply is in the system? Car unlocks with the fob and the red LED works, as it should.

Ah, and the alarm is triggered as well, when the fuel door is opened … obviously without ignition. Could it be the LH door lock on a LHD vehicle? Defective cdl switch? Or an error in the communication of this switch? Like broken wire, loose connector, error in the door outstation?

Another question I have: Is it possible to change the market settings with the Nanocom? I only found market set and not set, but no options to choose? I was told either setting to japan or canada will deactivate some not so much liked features in the alarm and immobilster e.g.
What diagnostic tool can set the market? I know faultmate, T4 …

To rule out the power supply as a source for triggering the alarm I asked the fellow to pull fuse 14 and see if the alarm sets of when the ignition is switched on. Fuse 14 powers the fuel flap, the rear cdl, trailer socket and tailgate cdl.
Will post result.
My hypothesis is that when the alarm does NOT set of, when the ignition is turned, the problems is in this circuit or signal processing in the BECM, if it still does, the search continues in another direction.

Alarm is still triggered with Fuse 14 pulled.

Finally spolved the strange problem ... after initially having the ignition barrel/lock under suspicion, we swapped the BECM to another one which has been programmed by a fellow enthusiast with the cars data (Keycodes, EKA etc.). Now everything works fine again. So sometimes it is really the BECM. Maybe we´ll find out wether it was the power board or the logic board of the BECM, but that is far beyond my personal capabillities. I just did the diagnosis and swapped the BECM and did some stuff with my diagnostics (synching EMS-BECM).