Headlights Staying On

[MacRS200]

Noticed this morning that the door open indication on the dash is now started working as well (added to list on my post above), the door switches connect into the Body ECU. And the Body ECU connects into the Theft Deterrent ECU controlling alarm and auto headlights.

[Motsey]

i sorted mine by removing all the plugs in the fuse box and also in the box behind the steering wheel(2 plugs) think thats the alarm/theft deterant ecu and then sprayed them (plugs and connectors) lightly with Electrical Solvent Cleaner from maplins and wiped throughly with tissue & microfibre cloth making sure i got into every hole and also left to dry over night and connected it back the following afternoon and it all worked (i made sure i disconnected the battery)

***** I am not telling anyone to try this or saying it will cure your car so if you do try this then i take no responsibility

for what ever may happen to your car ***************************************************************

[k33rjd]

aarronabott- had a look at the IS of my mates today with the lights on like yours. the fault lies with the windscreen- where the apost is welded together behnd the windscreen water seeps between the panels and down inbetween the chassis on the o/s. this makes contact with a number of different looms that run through there. the water then enters the junction/relay block in the footwell. you may not find any sign of water on the wiring as it wont stay there for long, what it does is pool in the bottom of the junction block and this shortens out the headlights turning them on when they sholdnt be.

to sort this you will have to get teh screen removed and sealant applied to the bottom lips of the apost where the roof meets the inner wing. then you can try to dry out the junction/relay block in the drivers footwell with a hairdryer. not too hot as you will cause damage. if it doesnt sort the problem then it will need replacing- £283+vat for the part in question.

macrs2000- if your horn is operating when its not supposed to, then your fault lies with the fuse/junction block in the n/s footwell. water drips from the scuttlepanel onto the wiring loom that enters the bulkhead, this allows water to travel down into the junction/fuse block and cause a number of faults from horns sounding, efi relays clicking repeatedly when car turned off, speedos not operating or operating when stationary. check the wiring loom for failed sealing of the wires- there should be a clear sealant in the center of the grommet. also if you have an amp cable running through here, check to make sure that this isnt the fault, if this is all sealed and in good order then agian the fault lies where the chassis requires sealing around the bottom of the apost (on the n/s in this case). allow the fuse/junction box to dry off and use a hairdryer if possible. if your still have faults then you may need to replace with new.

so in general- check your interior light switch for correct operation- key in the ignition (on position), drivers door open, interior light on door position- then press and release your door switch on the b-pillar (black rubber button). the interior light, drivers door warning light and light around the ign barrel should turn on and off as you press it in and out.

if this is ok then determin what fault you have-

headlights - o/s

horn -n/s

check for obvious water leaks-if none found get windscreen removed and resealed, ensuring plenty of sealent around a-post chassis joins. and dry out or replace junction/fuse boxes.

[MacRS200]

Interesting but why do you say the N/S footwell for the horn problem? in this DIAGRAM the horn circuit shows only the switch (on the steering wheel) and the theft deterrent ECU being connected, they are both on the O/S.

[aaronabbott]

I had every part that you have mentioned replaced by a qualified auto electrician which fixed the problem initially. Two days later the problem re-occured (bearing in mind this was the summer and there was no rainfall). A day after that the problem went and all seemed well and then it suddenly happened again.

Me and other members have taken my car apart piece by piece to try and locate the problem. We checked and cleaned each part individually to the extreme of even dismantling the fuse box to clean each seperate contact but we found that there was no corrosion present (that included theft ecu, door switches etc that were connected to the circuit).

[MacRS200]

Right I'm like a "dog with a bone now" and probably boring the pants off everyone

OK just tested the relay and it's OK, also tested that horn switch direct from the relay base in the engine bay fuse box. As expected constant 12V in one side of the coil and pressing the horn gives a short to ground that goes when you release the horn push so the switch is OK.

From the diagram posted above the only way the coil can be energised with the horn switch open is if the theft deterrent ECU is pulling the feed to ground. Or am I missing something here?

[aaronabbott]

Right I'm like a "dog with a bone now" and probably boring the pants off everyone

OK just tested the relay and it's OK, also tested that horn switch direct from the relay base in the engine bay fuse box. As expected constant 12V in one side of the coil and pressing the horn gives a short to ground that goes when you release the horn push so the switch is OK.

From the diagram posted above the only way the coil can be energised with the horn switch open is if the theft deterrent ECU is pulling the feed to ground. Or am I missing something here?

nope thats the exact way i see it.on mine the circuit is reversed (ign off=headlights on/ign on=headlights off)

its just finding where its grounding

[fitchett87]

After autoglass spending aprox £1500 at lexus derby on my is200 the lights are not working again!!! But lexus derby have let me a IS250 SR for the week, Happy days. Anyone got £19000 they fancy givin me?

[aaronabbott]

After autoglass spending aprox £1500 at lexus derby on my is200 the lights are not working again!!! But lexus derby have let me a IS250 SR for the week, Happy days. Anyone got £19000 they fancy givin me?

how long did it last?

so was it a poorly fitting screen again? it cant happen twice can it

[fitchett87]

Also the fuel gauge says empty, the seat belt light is flashing and the door open light is on too. .... ?

[aaronabbott]

Also the fuel gauge says empty, the seat belt light is flashing and the door open light is on too. .... ?

had all those faults too but they went after playing with the plugs, its just the lights now,

did you see the old fuse board to check the state of it inside

[fitchett87]

It lasted about 2 months, Lexus haven't looked at it yet because i only dropped it off yersterday

[aaronabbott]

It lasted about 2 months, Lexus haven't looked at it yet because i only dropped it off yersterday

do you know what work was done before at lexus

[fitchett87]

It looked dry and clean to me but i don.t like poking around with all them plugs.

[fitchett87]

New windscreen that was checked by the manager, new ECU new fuse box.

[MacRS200]

Update - Now tried all combinations of horn fuse and relay in/out, as I suspected the faults that I have are only present when the fuse and relay are both in place. I am also now down to the following list not working with the relay and fuse in: -

• Fuel Gauge
  
• Temp Gauge
  
• Charging light
  
• Manual gear indication
  
• Heated rear window
  
• And horn U/S
  

Conclusion so far is that the problem is only there when 12V is on the theft deterrent ECU input from the horn circuit, as taking either the fuse or the relay coil out of the circuit clears the faults. So have to go find the theft deterrent ECU and the right connector to have a check on that. Problem is it's bloody raining now so don't want to get anything wetter than it already could be!

Anyone with the same (or similar) problems tried taking out the horn fuse just out of interest?

[aaronabbott]

Update - Now tried all combinations of horn fuse and relay in/out, as I suspected the faults that I have are only present when the fuse and relay are both in place. I am also now down to the following list not working with the relay and fuse in: -

• Fuel Gauge
  
• Temp Gauge
  
• Charging light
  
• Manual gear indication
  
• Heated rear window
  
• And horn U/S
  

Conclusion so far is that the problem is only there when 12V is on the theft deterrent ECU input from the horn circuit, as taking either the fuse or the relay coil out of the circuit clears the faults. So have to go find the theft deterrent ECU and the right connector to have a check on that. Problem is it's bloody raining now so don't want to get anything wetter than it already could be!

Anyone with the same (or similar) problems tried taking out the horn fuse just out of interest?

im confused now,it even confused geoffers at the midlands meet

[MacRS200]

im confused now,it even confused geoffers at the midlands meet

That makes 3 of us then.

My logic WAS going this way: -

1/ The theft deterrent ECU can pull the horn relay coil to ground if the alarm was triggered, setting the horn off. If the ECU saw a false alarm it would lock the horn on (my inital problem).

2/ If you pulled the horn fuse or relay the ECU would know that the circuit had been tampered with because it no longer "saw" 12V on it's input and presumably activates the immobiliser.

I can see no other reasons for the connection.

Where I am now is at a dead end as I can't see a wiring fault to ground causing the problem as the horn would be on all the time so it must be the ECU. So why does 12V on the ECU cause all the other faults?

[loggyboy]

Furhter minor update on mine:

After having autoglass out on the the 19th feb to reseal it, today was the 1st sign of rain to test, however it was very light rain which never used to set it off, it had to be persistant heavy rain. HOWEVER the lights are on as we speak so it appears they have made it worse as they now come on with the tinyest amount of rain.

Awaiting a call back from them now.

[loggyboy]

Wooo extra rain means 3 new faults to add to the list... this evening I have had everything, lightson , alam set off when entering, no fuel, mpg, water temp gauges, outside temp showing 'E' - and now the added bonus of seatbelt warning light on, even when belted up, door open light on, rear screen demister not working even though light is on switch AND 'snow' indiciator light failing to come on when switch is pressed, (and possibly snow function not working either but its hard to tell!)

[Steviewevie]

Wooo extra rain means 3 new faults to add to the list... this evening I have had everything, lightson , alam set off when entering, no fuel, mpg, water temp gauges, outside temp showing 'E' - and now the added bonus of seatbelt warning light on , even when belted up, rear screen demister not working even though light is on swith AND 'snow' indiciator light failing to come on when switch is pressed, (and possibly snow function not working either but its hard to tell!)

Oh dear, that does sound like they've made things a lot worse now ! :duh:

[aaronabbott]

fitchett87 had his go again after autoglass spent aprox £1500 at lexus derby replacing everything on his car and the lights are not working again,ive pm'd him asking how he got on but got no reply yet,as mines becoming a real pain in the ar$e now(luckly its just the headlights)

[loggyboy]

Ive just got back from Autoglass bracknell, they wanted to check it again, however when i got there he just looked at the screen and said that was all he need to check. He had made some calls and found that the Pilkington branded screens have a possible fault with the heated element cables causing sealing issues. So theyve agreed to fit a genuine Lexus screen, just awaiting a call back when they have sourced the glass.

Im sure ive read somewhere here about problems with pilkington glass??

[kam05]

I always insist on replacement OEM glass.

Just before Christmas my NSF door glass was smashed, got Autoglass to source a OEM replacement from Lexus.

[fitchett87]

Ive just got back from Autoglass bracknell, they wanted to check it again, however when i got there he just looked at the screen and said that was all he need to check. He had made some calls and found that the Pilkington branded screens have a possible fault with the heated element cables causing sealing issues. So theyve agreed to fit a genuine Lexus screen, just awaiting a call back when they have sourced the glass.

Im sure ive read somewhere here about problems with pilkington glass??

I dont believe it thats what they have replaced in my car!!