Headlights Staying On

[aaronabbott]

a silly question but have you checked all of your fuses?

especially the- 120a alt, 7.5a ecu-b2, 10a ecu-ig fuses

the only thing thats really sticking out is the theft deterent ecu, this is controlled by the ign and in turns controls the lights.

fuses are ok

ive had a replacement theft deterent ecu before with fuse board and it fixed the problem for a few days, its just trying to source the bits again from breakers as spares just incase

[Steviewevie]

Have you pulled out the IH3 connector to see if it's corroded at all ?

[k33rjd]

ih3 goes to the instrument panel

[Steviewevie]

ih3 goes to the instrument panel

See above, it connects to the theft deterrent ECU too, which is part of this circuit.

[aaronabbott]

Have you pulled out the IH3 connector to see if it's corroded at all ?

heres the plug

the pins on the fuse board look as new

[Steviewevie]

How about the connector at the other end, i.e. at the theft deterrent ECU, is that ok too ?

[aaronabbott]

How about the connector at the other end, i.e. at the theft deterrent ECU, is that ok too ?

yeah all ok (both plugs that enter the anti theft ecu)

[k33rjd]

with ih3 unpluged are the lights still on or are they off? also have a look further up as u have ig1 on the same connector holder

[aaronabbott]

with ih3 unpluged are the lights still on or are they off? also have a look further up as u have ig1 on the same connector holder

cant remember i think they were still on,i cant play about play about with it now till wednesday

[Motsey]

Hi ive read the complete thread and am very dissapointed that there is no cure for it :-( was wondering if anyone has any good news as it has just happened to my car and yep i had a windscreen replaced not so long ago

Im going to check all connectors in a bit to see if that dose anything

[rig-pig]

the cure is for the windscreen to be fitted correctly

[Motsey]

**edit**

im going to rac windscreen on monday and the lights seem to be working ok today but i didnt chance leaving the relay in over night, dont fany a dead Battery in the morning

what should i tell the guy at rac windscreen to look out for just so he dose not waste hours looking at the screen and miss it

also he said if needs be he will refit the screen, should i get him to do that or just reseal it as it is?

-Thanks

[loggyboy]

Mine started doing this tonight :(

had my screen replaced a few months back but this is the 1st time ive had the problem. Its been ok for the last few hours but i dont fancy leaving it overnight to wake up to a flat battery, so may do the relay trick.

I even warned the guy from autoglass about the problem, stating, 'Ive heard from lots of owners club members that its a common fault after the screen is replaced and that the wire for the auto lights needs to be sealed well'

he assured me that it would be and that all work was warrantied anyway. PAH!

Il be checking my fuse box tonight and making a call to Autoglass 2moro morning if i find damp in there.

Just thought id update on mine:

After this happened in Dec, we had a dryish spell and it hadnt happened, untill we had all the snow last week, when that melted i had the light problem, it also went on to effect the Temp, fuel and MPG guage (all registerted 0 when driving) - then the final straw was the alarm!

I unlocked the car with the fob, and opened the door and the alarm was set off, and it would not go off no matter how many times I locked and unlocked it with the fob. Eventually it stopped, so I tried again, and it set off again! This time i just got in and drove, 100yrds down the road it stopped and didnt do it again, however the lights persisted till the rain stopped on monday.

I rang lexus who confirmed it was a common fault (i didnt mention screen and the moment i said the lights were coming on they imediately asked if id had the screen done.) They recommended i took it back to autoglass.

Took it there today and they 'water tested' it, (which consisted of little squirt from a hose) which revealed no obvious leak, however they have agreed to reseal the the screen next week.

So it will have to be a suck it and see situation.

Im going to start a simple thread to see how many have had this issue and what the outcomes have been.

Dave.

[Steviewevie]

Unfortunately the bit about the alarm makes sense in that the ECU for that is all connected up with the auto headlamps etc.

[MacRS200]

OK not posted on this thread yet as nothing useful to contribute till this morning, bear in mind this a Tezza not an IS but similar symptoms. The car also has has an after market TOAD alarm/immobiliser.

List of things U/S

• Fuel Gauge (Flashing Light)
  
• Temp Gauge
  
• Rear Defogger
  
• Outside air temp indicator
  
• Air Con on Automatic (Worked on manual)
  
• Tiptronic Gear indication
  
• Snow button
  
• ECT Power button
  
• Charging indicator light on dash
  
• Door Open Indication on dash (Added)
  
• + more I did not even notice probably
  

Cutting a long story short I started the car and hit the horn by accident putting my seat belt on this morning and the effin horn stayed on, popped the bonnet and pulled the horn fuse and the horn kept going. Next I took out the horn relay and finally the horn stopped Thank FFT I thought. Then what now, FFS the engine had stopped so put the fuse back in, lid back on the fuse box and shut the bonnet. Went to open the drivers door and it's locked, keys in the ignition and turned on, with the demister fan running (as it was on manual to defog the screen)! The car had locked all the doors!

Got the spare key after a while (another long story) and got the car unlocked, fired it up and well B***ER me all the stuff on the list above was working as normal. The only difference is that the horn relay is still out.

Ploughed through a the wiring diagrams and find that the horn fuse also provides a feed to the "theft deterrent ECU", the horn wiring is a simple ground through a switch. Tested the relay and it's OK so the only way to ground is through the "theft deterrent ECU"!

As pointed out above the "theft deterrent ECU" also controls the headlights, it's also connected to the "body ECU" (2 of) that control the rear demister plus other stuff.

That's far as i've got so far but will post back when I have any more.

Edited February 13, 2009 by MacRS200

[aaronabbott]

are your headlights still ok neil?

im starting to really despise these cars electrically wise nothings ever straight forward or easy to fix cos of this fecking theft deterrant ecu

[MacRS200]

are your headlights still ok neil?

im starting to really despise these cars electrically wise nothings ever straight forward or easy to fix cos of this fecking theft deterrant ecu

Yup headlights are fine, they are manual so I don't have the sensor wired into the "theft deterrent ECU".

[aaronabbott]

are your headlights still ok neil?

im starting to really despise these cars electrically wise nothings ever straight forward or easy to fix cos of this fecking theft deterrant ecu

Yup headlights are fine, they are manual so I don't have the sensor wired into the "theft deterrent ECU".

ok,have you disconnected the theft deterrant ecu to see if all the faults are still there

[MacRS200]

are your headlights still ok neil?

im starting to really despise these cars electrically wise nothings ever straight forward or easy to fix cos of this fecking theft deterrant ecu

Yup headlights are fine, they are manual so I don't have the sensor wired into the "theft deterrent ECU".

ok,have you disconnected the theft deterrant ecu to see if all the faults are still there

All the faults are gone for now with the horn relay out, was going to put it back in tonight but it's snowing round here. Target at the moment is the "theft deterrent ECU" as it seems to be the common link with all the faults.

[aaronabbott]

are your headlights still ok neil?

im starting to really despise these cars electrically wise nothings ever straight forward or easy to fix cos of this fecking theft deterrant ecu

Yup headlights are fine, they are manual so I don't have the sensor wired into the "theft deterrent ECU".

ok,have you disconnected the theft deterrant ecu to see if all the faults are still there

All the faults are gone for now with the horn relay out, was going to put it back in tonight but it's snowing round here. Target at the moment is the "theft deterrent ECU" as it seems to be the common link with all the faults.

when you were asking about removing the fuse board and stuff did you have the faults then?

[MacRS200]

are your headlights still ok neil?

im starting to really despise these cars electrically wise nothings ever straight forward or easy to fix cos of this fecking theft deterrant ecu

Yup headlights are fine, they are manual so I don't have the sensor wired into the "theft deterrent ECU".

ok,have you disconnected the theft deterrant ecu to see if all the faults are still there

All the faults are gone for now with the horn relay out, was going to put it back in tonight but it's snowing round here. Target at the moment is the "theft deterrent ECU" as it seems to be the common link with all the faults.

when you were asking about removing the fuse board and stuff did you have the faults then?

Yes, thought it was water in the drivers foot well fusebox as it pointed that way till the horn thing this morning.

[aaronabbott]

are your headlights still ok neil?

im starting to really despise these cars electrically wise nothings ever straight forward or easy to fix cos of this fecking theft deterrant ecu

Yup headlights are fine, they are manual so I don't have the sensor wired into the "theft deterrent ECU".

ok,have you disconnected the theft deterrant ecu to see if all the faults are still there

All the faults are gone for now with the horn relay out, was going to put it back in tonight but it's snowing round here. Target at the moment is the "theft deterrent ECU" as it seems to be the common link with all the faults.

when you were asking about removing the fuse board and stuff did you have the faults then?

Yes, thought it was water in the drivers foot well fusebox as it pointed that way till the horn thing this morning.

did u find any signs of water?

[MacRS200]

did u find any signs of water?

No dry as a bone.

[aaronabbott]

did u find any signs of water?

No dry as a bone.

strange that its exactly the same as mine.and nobody is any closer to solving this,its gotta be something silly

[MacRS200]

From what I can make out the theft ECT and body ECUs are all behind the dash near the drivers A pillar, also one of the connectors for the horn circuit that splits the feed from the horn relay coil between the horn switch and the theft ECU. So I am betting on water in that area ATM.