Mk3 Alarm Problem

[JackLS400]

Afternoon gents!

Long-time lurker, this forum has been an immense help to me over the past 6 months.

I purchased an L-reg LS400 last year for not lots of money and have had no end of problems with it. I've changed the front upper control arms, brake pipes, gearbox mount, EGR pipe... this particular car seems to have all of the 'common' problems, but so far I've been pretty detemined to get it sorted and turn it around.

A couple of months ago I put a new alternator on it (another 'common' problem), and a couple of days ago suffered complete Battery failure. Wouldn't hold a charge, even left trickling overnight wouldn't start the car.

I've just this evening been out and bought a new Battery and now my alarm fob doesn't appear to work so the car is now immobilised. I'm pressing the button, the little light flashes... and nothing happens. It has worked in the past, as we disconnected the Battery to put the new alternator on. I've whipped the fob out and the Battery tests 11.7v across it, which I assume is enough?

Any help would be very very gratefully received. My alarm fob looks like this:

The last three letters of the numberplate are TOS, which is becoming more and more appropriate the longer I have it!!

[JackLS400]

I forgot to mention: I jump started it this afternoon successfully, hopefully I haven't toasted any electronics!

[Tulpen]

This may or may not help.

When I had a Mk 3 my wife called me to tell me that 'she couldn't get the fob to work'. When I got to her she had the same indications as you - press the button, the light flashes, but the doors wouldn't open.

After messing around for a while I found that the little slide on the side of the fob had moved slightly. I moved it back and forth (exercised) it and tried again - it worked. I can't remember which position is which so you have to try it both ways.

If, however, you have inadvertently 'altered' the sequencing of the alarm or, have fried some of the electronics, then that is outside of my sphere of expertise. I'm sure, though, that somebody on here will be able to help.

[crow1342]

i had same problem tried all things but in end had alarm took out cost me £60

[oldhazey]

I had the same problem with my mark three,battery had gone flat from standing as they do,so full 24hr charge,bunged it back in and allsorts of bizzaire stuff happened !! any way i disconnected the Battery for 10 mins then reconnected,and all was fine again,and has been since.

[Malc]

I have had a Mk1, Mk2 and now my Mk3 Ls400 and i don't recognise your remote fob at all !!!

Is it correct for your car ?

Malc

[Maduggo]

Same question as Malc, is that a Lexus fob, not seen one like that before.

[Tulpen]

I had a 1994 LS 400 with exactly the same key fob...........and it worked very well for 15 years (OK, I changed the fob Battery a few times).

I've mentioned somewhere else on the forum that a Lexus Dealer (Glasgow) told me that some LS 400's had non-standard alarm systems fitted because a particular batch of OEM alarms didn't comply with Post Office Transmission regulations. How true that is, is anyone's guess.

The non-standard alarms were British and had a second, small, plug-type key. This could be inserted on top of the under-bonnet unit; a quarter turn of the key resulted in a 'de-sensitised' alarm system. I think it switched off the motion sensor.

[JackLS400]

Morning gents. Having done some research I can tell you that this is a Scorpion 5000 (also called a 918) alarm; fitted to mk3s for a period of about six months, and also fitted to a lot of Volkswagens of the same era. Scorpion have now gone out of business and were bought up by Cobra.

From what I gather, they are not fantastic alarms, and there are many people suffering from the same problem as I am. For example, this guy and this guy.

Tulpen, I believe the keyhole on the sounder just disables the sounder unit; the alarm will still flash the indicators and immobilise the car once activated.

I've found some instructions to remove it from an LS400 here, but I won't be doing this. I'm afraid this alarm issue has been the straw that broke the camel's back, and is the latest in a long line of problems that I have had with the car, so it is now on eBay.

Thanks everyone for your help, very much appreciated.

[run132]

Yes, that is indeed the fob for the Scorpion alarm. The alarm has been the only week spot of my car (and has nothing to do with Lexus/Toyota of course!). Mine does not like the cold! It refuses to unlock on the fob (or respond in anyway!) if the car is left locked outside overnight and temp falls below zero! If it was kept outside on a regular basis then I would have ripped it out and replaced it by now but I can work round it when I can.

Hope you manage to find a suitable replacement LS.

[555Ltd]

Hi all I too have had loads of probs with that alarm even when I worked at main dealers it was fitted to early ls400ucf20 and was a cat1 alarm but as in previous posts the company went bust and you cannot get parts anymore. It has a rolling code and the switch on the side of the fob is to turn on /off interior protection.they can lose cpde if Battery goes flat and there are various ways to resync (not all successful!!) I have bypassed quite a few but no alarm but car starts.alarm was originally fitted at import centre after coming off the boat.later ls400 had different fob and used toyota tvss system with extras fitted here to make it cat1

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