Corolla Rear Fog Lights

[Stujb]

Hi all,

I have a odd problem with my 2000 Corolla 1.4. Sometimes, not all the time, when I turn the headlights on the rear fog light turn itself on at the same time. I have checked the wiring and replaced the fog light switch. There is no sign of any repairs to the loom.

Has anybody else had this fault? Any suggestions?

[richard.c]

Hi,

Not actually seen the 2000 layout, only the 2002-6 one - is the fog light switch on the main lights stalk or a separate switch on the dash ?

As you have changed the switch and checked the wiring around the dash I would suspect something is shorting across the rear sidelight line onto the foglight line in the rear clusters - could be moisture or a loose stand of wire on either of the rear cluster connecter etc.

Can you get the fault when the engine is not running, ie vibratiion issue / short?

Can you get the fault when just the sidelights are on ?

[Stujb]

Hi,

is the fog light switch on the main lights stalk or a separate switch on the dash

Can you get the fault when the engine is not running, ie vibratiion issue / short?

Can you get the fault when just the sidelights are on ?

Thanks for the reply,

The fog light switch is a seperate switch in a little cluster with the mirror adjuster.

Yes, the fault happens with or without the engine running.

Yes it comes on with the side lights, I have no way of knowing if it comes on with dipped beam as I have to turn the sidelights on 1st.

The great bit about this is I worked as a Toyota Tech from 1995 to 2000 and bought this car thinking 'better the devil you know'. I left just after this model came out so I have no real experiance, I just wondered if it was a known fault as the British built Toyota's were more problematic than the Japanese built models

[ricc]

the vcar ever had a tow bar fitted and/or subsequently removed?

[Stujb]

I've had a look and can't see any signs that a tow bar was fitted (no splicing into the loom or holes/marks underneath where the bar would have been fitted). All the looms looks like the original ones and the car is completely standard apart from me fitting a CD player. The fault was happening before I fitted the radio.

I think I'm going to be stripping the cars interior when the weather improves to try and find this fault

[richard.c]

Thanks for the reply,

The fog light switch is a seperate switch in a little cluster with the mirror adjuster.

Yes, the fault happens with or without the engine running.

Yes it comes on with the side lights, I have no way of knowing if it comes on with dipped beam as I have to turn the sidelights on 1st.

The great bit about this is I worked as a Toyota Tech from 1995 to 2000 and bought this car thinking 'better the devil you know'. I left just after this model came out so I have no real experiance, I just wondered if it was a known fault as the British built Toyota's were more problematic than the Japanese built models

Hi,

Well if you have replaced the switch that should eliminate any problem there.

Another simple test to eliminate things.

Assume your switch has the red led on it as well.

With the fogs switched off I would disconnect the cable connectors from both rear clusters and then turn on the sidelights and see if the led in the fog switch comes on.

If it does your fault is in the wiring, if not then something is shorting in the rear clusters

[Stujb]

Assume your switch has the red led on it as well.

No the fog light 'on' light is in the cluster. The biggest problem is that it only happens every other time, not every time I turn the lights on, when it does not happen it does not happen at all. My initial thought was the relay which appears to be part of the switch, as that is where the click is coming from.

I get the feeling my forehead and a wall will be connecting a lot sorting this one.

[ricc]

do the corollas run separate circuits or do they run a multifunction box for all the lighting/ancillaries? if they have an MFU, a fault in that could explain the erratic behaviour. if they're separate circuits it just does'nt make sense.

[Stujb]

do the corollas run separate circuits or do they run a multifunction box for all the lighting/ancillaries? if they have an MFU, a fault in that could explain the erratic behaviour. if they're separate circuits it just does'nt make sense.

Are you on about the newer systems? Toyota/Lexus call it multiplex, Ford the BUS system etc? Then no, it's good old fashioned'ish stuff.

And your comment is spot on 'if they're separate circuits it just does'nt make', you're right, it does not make sense at all, hence my head banging comment further up the thread.

I'm guessing from your responses, though I have only just posted this afternoon, that this is not a common fault. I shall find it, that or a gallon of petrol and some matches :o

I will post the result of my find, that or I'll post the pic of the burnt out carcase.

[ricc]

checked the light circuit board for the rear cluster for corossion/freyed/extra wires?

[jw67]

do the corollas run separate circuits or do they run a multifunction box for all the lighting/ancillaries? if they have an MFU, a fault in that could explain the erratic behaviour. if they're separate circuits it just does'nt make sense.

Are you on about the newer systems? Toyota/Lexus call it multiplex, Ford the BUS system etc? Then no, it's good old fashioned'ish stuff.

And your comment is spot on 'if they're separate circuits it just does'nt make', you're right, it does not make sense at all, hence my head banging comment further up the thread.

I'm guessing from your responses, though I have only just posted this afternoon, that this is not a common fault. I shall find it, that or a gallon of petrol and some matches :o

I will post the result of my find, that or I'll post the pic of the burnt out carcase.

Well it's common with mine and it's :censor: annoying.Mine does it all the time now but "flicking"the switch lightly continually will eventually switch it off until I 'hit'the slightest bump in the road.I thought a new switch would cure it but now you've got me thinking.

At the moment I've removed the bulb in the rear lights but this is far from ideal.

[ricc]

relay failure?

[Stujb]

jw67, happens over bumps? Mine only does it when I turn the lights on.

I'm going to have a chat with a dealer or 3 tomorrow, see if I can get any sense out of them.

ricc, all the boards look ok and I think the relay is in the switch which both myself and jw67 have swapped. I suppose if it is a common fault then it's possible the switches are faulty as I got mine from a breaker, where did you get yours from jw67?

[jw67]

jw67, happens over bumps? Mine only does it when I turn the lights on.

I'm going to have a chat with a dealer or 3 tomorrow, see if I can get any sense out of them.

ricc, all the boards look ok and I think the relay is in the switch which both myself and jw67 have swapped. I suppose if it is a common fault then it's possible the switches are faulty as I got mine from a breaker, where did you get yours from jw67?

I haven't replaced mine yet,but I have read about it on here before and followed other Corollas with the rear foglight blazing away which I presume have the same problem.

As for the "bumps"part of my post,what I mean is when I switch lights on the foglight comes on,flicking the switch can turn the light off but sometimes bumpy surfaces bring it back on again.Sometimes,like tonight,it never came on when I drove home from work :ffs: .

Main dealer prices are ridiculous but,at least the part should be guaranteed to fix the problem.

[Alastair Robertson]

Hi ... I have a W reg (2000) 1.4 vvti Corolla Vida (dark blue if that is of interest!).

I noticed when I first got it back in 2009 that the rear fog light often came on by itself. I noted that if it were to come on, it would only do so when the headlights were on and within the first few minutes of getting into and driving the car. I thought that I might have been nudging the switch with my knee, but no matter how carefully I got it, there it was a few minutes later - on!

I removed the fog light switch from the dash, and being compentant with electronics dismantled it for a look see. Nothing appeared to be wrong, but there were some electrolytic capacitors in there and these types of components are known to be liable to degraded performance after a few years, especially if they have been exposed to extremes of temperatures. I figured "what the hell" and bought a new switch from Toyota.

This cured the problem, until last week; so the fix lasted about two or three years.

I just happened to notice what triggered the issue this time ... and it is repeatable ... which is why I thought I should share it with this forum.

My rear fog light comes on under these conditions:

> The headlights must be on

> I must have been in/driving the car for LESS THAN 2 minutes

... I must brake ... and then the fog light comes on when I RELEASE the brake pedal.

Conclusion .... a voltage variation, or spike, caused by the brake lights turning off can trigger the fog light to turn on within the first minutes of driving, if the headlights are on.

Thanks goodness ... I thought I was going mad!!

Now I need to find a circuit diagram and/or inspect the wiring layout to see what the interplay is between the braking light circuit and the fog light circuit ... watch this space.

Cheers

Alastair

Have now found circuit diagram and as far as I can see the only common point between the fog & braking circuits is the grounding points (left and right hand sides) near the two rear light clusters.

I will investigate and report back in a week or so.

Edited March 19, 2012 by Alastair Robertson

[klyota]

I'm having exactly the same problem as you, did you ever find out what the problem was?

Also my headlights sometimes turn off intermittently, already had my headlight switch replaced but this did not

solve the problem. I wonder if the two issues (foglight coming on and headlight turning off) are related?

Mine is 1 1.4 2001 Corolla.

Thanks,

James