Electrical Problem

[Mr Morse]

I was driving around towm a couple of weeks ago, when the nearside indicators started double flashing. Having no idea what was causing this I continued to drive, looking for somewhere safe to pull off the road. All of a sudden the engine just cut out amd would not restart. I had to push the car into a bus stop. Embarrasing!

Switching the engine off failed to stop the indicators. Removing the two ECU fuses in the engine fuse box didn't work. Disconnecting the Battery did stop the problem.

I reconnected the Battery and drove back home. After checking all the wiring on the indicators (including the load resistors that are fitted to prevent the LED's overflashing) I couldn't find any obvious root cause.

However......for some reason the horn would not work!

I was out again today, and the same thing happened again, in town, after driving on the motorway fro about 1 hour.

Immediately I opened the bonnet and could hear a clicking noise from the horn relay in the engine fuse box. I disconnected the Battery to reset the ECU. I did not replace the relay, thinking it may be the cause of the problem.

After driving off again, same problem occurred. This time after disconnecting the Battery, I replaced the horn relay.

Drove off again, no repeat of the indicator flashing problem, but the horn still does not work.

This is all very wierd.

1) Are the nearside indicator flashing problem and the failed horn part & parcel of the same problem?

2) Why does this problem cause the engine to cut out?

3) After resetting the ECU by disconnecting the Battery, it took almost exactly 1 minute for the problem to reoccur

4) Why do only the nearside indicators (front/rear/side) all overflash, why not the offside?

5) Is this something to do with the LED bulbs?

6) How do I check if the horn relay has failed?

7) Only happens at low speeds <40mph

8) Is there anything obvious I'm missing here?

[TTE200]

am new ot the Lexus and it sound like you know more then me.

just thought but could this not be a problem with the car alarm, as the indicators and horn form part of the car alarm along with an immobiliser which would explain why the car is cutting out.

[BAGGY]

I think tte200 is on the right track there do you know if the alarm and immoblizer

are part of the same control unit?and dose the left and right indicators work as

normal when the fault isn't present.As for checking the horn relay press the horn

with ignition on and feel with your fingers if its moving inside and if it clicks.

[Mr Morse]

I'm doubting that this problem is alarm/immobiliser related purely because only the nearside indicators are affected and the remote operates the central locking / alarm exactly as it shoud do.

The indicators work fine when thisn problem does not occur.

Anyway....keep the suggestions coming please!

[MrADeveci]

Tried posting on .net mate?

[waddy]

Obviously my suggestion is as useless as mudflaps on a tortoise until the new year but the stealer should be able to run a diag check on her.

Low speeds suggests something may be getting hot somewhere - don't know what it could be though - ECU gone bananas?

[Mr Morse]

Obviously my suggestion is as useless as mudflaps on a tortoise until the new year but the stealer should be able to run a diag check on her.

Low speeds suggests something may be getting hot somewhere - don't know what it could be though - ECU gone bananas?

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Problem there Mark - the only way to clear the problem is to disconnect the Battery, which clears the ECU diagnosic codes

[waddy]

ECU should keep the cosed logged shouldn't it? Does it not have a BIOS type thingy in it? Is there a difference between a hard ECU reset and a soft?

Don't know - I'm just guessing.

[Mr Morse]

ECU should keep the cosed logged shouldn't it? Does it not have a BIOS type thingy in it? Is there a difference between a hard ECU reset and a soft?

Don't know - I'm just guessing.

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Removing the two fuses will keep the codes, disconnecting the Battery clears the ECU

[Monster-Mat]

in all honesty as has already been suggested i think its part of the alarm/immobiliser thats at fault

its possible that the resistors is causing the theft ecu to think theres a fault.

the indicators/horn are part indirectly of the theft system

[MrADeveci]

Removing the two fuses will keep the codes, disconnecting the battery clears the ECU

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Removing the two fuses, or disconnecting the Battery does the same thing mate ........... both resets the ECU, and clears the codes !

[Mr Morse]

Removing the two fuses will keep the codes, disconnecting the battery clears the ECU

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Removing the two fuses, or disconnecting the Battery does the same thing mate ........... both resets the ECU, and clears the codes !

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No - pulling the fuses will retain the codes

[Monster-Mat]

Removing the two fuses will keep the codes, disconnecting the battery clears the ECU

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Removing the two fuses, or disconnecting the Battery does the same thing mate ........... both resets the ECU, and clears the codes !

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No - pulling the fuses will retain the codes

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pulling both will clear the ecu, but you need to wait minimum of 5 mins, for the short term memory to be lost from the ecu

Edited December 24, 2005 by Monster-Mat

[Lexus Jim]

maybe try taking the leds out and putting normal bulbs back in and see if the problem still occurs. this would at least eliminate them?

[Mr Morse]

One of the very helpful guys on IS300.net is convinced it's a failed horn relay......soon as I figure out how to check the relay

[Monster-Mat]

One of the very helpful guys on IS300.net is convinced it's a failed horn relay......soon as I figure out how to check the relay 

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if you need a relay i have a few spares, you should hear it clicking when powered up mike

[Mr Morse]

OK then, I've got to the cause of the problem:

The car is fitted with an aftermarket horn, which has it's own relay switch. Something had loosened the relay from it's mounting point and had cracked. This had allowed water into the relay, causing a short circuit.

I've changed out this one and fitted a new 30amp relay and the problem has been cured.

This was really doing my head in!