I hope someone out there can help!

My GS300 has developed a fault with the brake lights, they don't work!

I checked the 20A fuse in the drivers footwell, it is OK.

I checked both bulbs, they are OK.

I removed the under dash panel (with the footwell light & diagnostic socket) to see if I can see anything unusual, nothing I can see, switch moves when the pedal is pressed.

Is there a relay I can check?

My thought is both lights = fuse, relay, switch or wiring.

Any ideas to try and diagnose this dangerous fault?

Cheers,

Mark 8-)

If the cruise control is working then you could set it to cruise. If the cruise control cancels when you press the brake, then that proves the switch ok or not. There are no relays that I know of for the stop lights only the 20amp fuse you have checked. Although the 15A "gauge" fuse does power the light failure sensor circuit, so maybe worth a check just in case. Other than chasing the power, not much else I can think of. Do any warning lights come on to indicate it thinks there is a blown bulb?

Hi,
Although the brake light switch physically moves/operates this is not an indication it is working electrically,the contacts in the switch could be faulty.
If you have a digital meter it is fairly easy to check for a 12v supply to the switch then press the brake to operate the switch and make sure the 12 v appears at the other connection.
Another test is to remove the 2 wires to the switch then connect them together with a piece of wire and then see if the brake lights come on if they do it is the switch.

Thanks guys,

I am off to the car to see if the switch is at fault, as suspected.

I will keep you informed.

Mark 8-)

Just removed underside of dash (only 7 screws in all) to reveal brake pedal switch.

Removed switch and tested with multimeter. Appeared to be faulty at first, but with a bit of rapid pressing it works, might be a recurring fault so I will source a new switch and replace when I have it.

Checked the electrical circuit to the brake lights by shorting the 2 small and 2 larger terminals of connector together, resulting in working brake lights.

Refitted switch to connector and checked brake light function by pressing switch before re-fitting to the brake pedal assembly. A bit of adjusting to get required function of switch when back in place, but now brake lights are working with brake pedal.

Put it all back together and in all it took about an hour of fiddling about to get the brake lights working again.

All in all, Lexus made the GS300 fairly easy to work on, on this occasion.

Mark 8-)

[quote name='Fat Dad' timestamp='1288110683' post='736402']
All in all, Lexus made the GS300 fairly easy to work on, on this occasion.

Mark 8-)
[/quote]
Yup, on this occasion. You won't say that when you want to change the spark plugs

Glad it is sorted.

Any ideas where to get my replacement switch?

Was going to do the Google search to see what I can come up with.

Cheers,

Mark 8-)

[quote name='Fat Dad' timestamp='1288119566' post='736424']
Any ideas where to get my replacement switch?

Was going to do the Google search to see what I can come up with.

Cheers,

Mark 8-)
[/quote]

I would start by PM'ing the user ACLex on here, he is at Lexus Poole and normally does some good prices. Failing that, there are lots of Mk1's breaking on ebay that you could try contacting.