immobiliser wont disarm

1995 300Tdi

Got an intermittent problem - sometimes i cannot unlock the car and disarm the immob with the fob. It's got new batteries and when it works, will disarm from quite a distance.

So, it's armed now, and blaring away as I had to move it for swmbo so she could get to work.

Where should i start looking to fix this? I'm pretty sure its not the fob as it's in good condition, new batteries and not got anything loose inside.

I'm not looking to bypass it particulalry as the alarm/immob is useful.

Thanks

Would that be a single or a two button fob? .. single buttons can be re-programmed by the user, two button fobs can go out of tune ie off frequency. Go to Remotekey's site for more info.

discool said:

Would that be a single or a two button fob? .. single buttons can be re-programmed by the user, two button fobs can go out of tune ie off frequency. Go to Remotekey's site for more info.

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It's a single button style. I've reprogrammed several times. It seems to work fine for a while then stops working (always when locked lol). After a while of not working, it starts working again.

If you have a leaking sunroof it could be the sensor in the roof, mine failed i now keep a spare in the glove box
Mark

mark-ypvs said:

If you have a leaking sunroof it could be the sensor in the roof, mine failed i now keep a spare in the glove box
Mark

Click to expand...

Only disco 2's have a sensor in that position.

j_rov said:

It's a single button style. I've reprogrammed several times. It seems to work find for a while then stops working (always when locked lol). After a while of not working, it starts working again.

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I doubt it's the alarm unit, but have a look at to see if the multi pin plug is pluged in fully and the antenna is also that will have a coax tv style plug.
Alarm unit is behind the glovebox.

no sunroofs in mine anyhow...

discool said:

I doubt it's the alarm unit, but have a look at to see if the multi pin plug is pluged in fully and the antenna is also that will have a coax tv style plug.
Alarm unit is behind the glovebox.

Click to expand...

thanks, I'll whip it all apart tomorrow and have a look.

beginning to do my head in!

If i unplug, clean and replug will it wipe memory or worse?

discool said:

Only disco 2's have a sensor in that position.

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Discovery 300 tdi has it aswell 2 button remote and sensor up near interior light
but i did post before i sae the single button reply
Mark

mark-ypvs said:

Discovery 300 tdi has it aswell 2 button remote and sensor up near interior light
but i did post before i sae the single button reply
Mark

Click to expand...

You did say "could be sensor in the roof", the tread is about communication between the fob and the alarm ecu and not false alarms due to the ultrasonic movement sensor located below the headlining.

So the D1 does NOT have a sensor in the roof but the D2 does

discool said:

You did say "could be sensor in the roof", the tread is about communication between the fob and the alarm ecu and not false alarms due to the ultrasonic movement sensor located below the headlining.

So the D1 does NOT have a sensor in the roof but the D2 does

Click to expand...

The thread is about 'Got an intermittent problem - sometimes i cannot unlock the car and disarm the immob with the fob'.
When i had this fault with mine it turned out to be the roof sensor (ultrasonic) if the sensor fails (mine was intermitant)the doors wont unlock from the remote and the imobilliser will not disarm, i could unlock the doors with the key but it still woundnt start, i removed the ultrasonic sensor as it was full of water and replaced it now the doors unlock at the car starts?? and i now carry a spare
So my conclusion was the roof ultrasonic also disables the immobilliser but i could be wrong ( not for the first time)
Mark

How do you reprogramme the single button remote

sebborn1 said:

How do you reprogramme the single button remote

Click to expand...

Just search "reprogramme a single button fob".