LS400 remote key issue

Gorodish2022 · March 9, 2023

Hi everyone, hello again. I was a member years ago, and have recently returned to the LS400 fold (I missed them too much!) getting a 1998 DHP in Bronze from a lovely chap in Cheshire.

Anyway, one niggling problem that you all may be able to solve. The remote locking has become weaker and weaker recently. Thought it was the key Battery, but replacing this yesterday made no difference (I’ve got all the keys plus the Master). They are all the same, weak and hit/miss. Transponder seems ok, it will start ok when I get in.

Is there a separate local Battery for the remote locking in the car itself that gets knackered after 24 years?! Like the system Battery on a laptop? Or any other suggestions?

thanks in advance

Malc1 · March 9, 2023

Tom welcome to this amazing forum . everyone's friendly and will help where possible I know

Can you tell us more about your new purchase . might it be something we already know about, this specific car, from prior thoughts on this forum ?

We love to know about mileage, regn and all else, were very very nosey 😆

Your problem .. when was the main Battery last changed .. could it be that maybe ?

Malc

Gorodish2022 · March 9, 2023

Hi Malc, thanks for the welcome. It’s a great forum.

This is my 4th (!) LS400, a car that seems to continue to call to me! It’s had an excellent previous owner who has done a huge amount of work; suspension, brakes, bodywork etc.

182k miles, tan interior, everything works apart from the aerial and the LED illumination in the temp display (I seem to remember there is a fix).

I’d have suspected the car Battery but it is a relatively new Bosch and putting out a decent charge.

I’m hoping I can avoid taking it to Lexus Cheshire Oaks….I live in a relatively low crime area but still feels wrong leaving it unlocked (to be on the safe side).

All ideas welcome!

Gorodish2022 · March 9, 2023

N40LEX btw

Malc1 · March 9, 2023

I've not seen your specific car mentioned here before N40LEX so that's a good sign I guess 😅

Maybe an auto-electrician should look at it for you ..... might be £££££ less expensive than the Main Dealer who might not have a clue, relying on a specialist for advice anyway !

But the joy I had in finding a competent auto-electrician local to me was woeful tbh

Malc

steve2006 · March 9, 2023

IIRC the receiving aerial for the remote locking/unlocking is the rear window de-mister element so check that for any damage or stuff on the parcel shelf.

The receiver (again from memory) is located in the passenger side boot area behind the trim.

The receiver aerial plugs in to this.

Remove the aerial plug then put the metal blade of the key into the socket without touching the sides, press the fob keys and see if they work.

If they do suspect the receiver aerial or cable if not working either the fob (unlikely) or receiver unit.

You would be lucky to find a replacement receiver if faulty plus complete key reprogramming would be required so a 3rd party replacement option may be the best option.

While in the boot check the spare wheel well for water ingress which could be causing damp issues with the electronics, the boot seal being the usual culprit.

rich1068 · March 9, 2023

2 hours ago, Gorodish2022 said:

I live in a relatively low crime area but still feels wrong leaving it unlocked (to be on the safe side).

Can you not lock and unlock with the key? My LS had no fob at all when I first got it and until I sourced one I just used the key in the driver's door.

5 hours ago, Gorodish2022 said:

Hi everyone, hello again. I was a member years ago, and have recently returned to the LS400 fold (I missed them too much!) getting a 1998 DHP in Bronze from a lovely chap in Cheshire.

2 hours ago, Gorodish2022 said:

N40LEX btw

That'll be Rich Scott's old car. He's never been a member on here but he's a good friend of mine.

Gorodish2022 · March 9, 2023

Yes, I bought it from Rich. Top guy!!

Gorodish2022 · March 9, 2023

The-Acre · March 9, 2023

Majestic or what!

Razor61 · March 10, 2023

23 hours ago, steve2006 said:

While in the boot check the spare wheel well for water ingress which could be causing damp issues with the electronics, the boot seal being the usual culprit.

Couldn't agree more and check the side areas in the boot under the side flaps. The inner arches can rot through at the bottom so water gets in and if really bad it can continue all the way up the inner arch.

Gorodish2022 · March 10, 2023

The boot appears dry, it has rotted out previously and the car has has a pretty penny spent on rust repair and an excellent part re spray.

It isn’t a binary issue, the remote range just seems to have reduced. It usually works in the end but not in that confident way from halfway across the car park that we all love!! It could be the weather. Will try taking things apart as Steve helpfully described, when the weather is a bit better.

Supafly · March 10, 2023

I remember reading somewhere that the key's are designed to work a short distance from the car. I'll see if I can find the source...

It may be that yours was an over achiever in this regard before.

Would be interesting to find out what other peoples experiences are of 'the range'.

ambermarine · March 10, 2023

The range on my Mark 4 is about a hundred feet(30metres),uninterupted view.

Gorodish2022 · March 12, 2023

Mystery solved. Both the keys were faulty in different ways. One clearly has a loose connection which makes it unreliable. The other’s Battery was flat! Both having similar symptoms, I put 2 and 2 together and got 5.

Minor faff to change the batteries as both had knackered screws, but all good in the end.

Thanks to all for your ideas. T

BigBoomer · March 14, 2023

By the way, if you want to increase the range of your remote key, hold it next to your head.
Yes, it works and surprisingly well too, but you do look a bit of a numpty. 🤣

Supafly · March 14, 2023

On 3/10/2023 at 5:06 PM, ambermarine said:

The range on my Mark 4 is about a hundred feet(30metres),uninterupted view.

mine was only 5-10 meters max (clear view also) even with a new Battery.

I've done the hold next to head/under chin before and it did work 🙂

Scribe · March 14, 2023

My unlock button is a bit iffy - I often have to keep pressing it hard - while the unlock one is always fine. Maybe need a new remote, or can one button be adjusted/repaired? For a while I used a combination of remote and key locking/unlocking but that eventually confused the electrics, or so it seemed, because one day it set the alarm off. A quick disconnect of the Battery re-set everything.