Toyota Aygo 1.0 petrol 57 MMT semi-auto - Aygo engine management warni light on when braking

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Sat 16 Jan 2016 09:54
Toyota Aygo 1.0 petrol 57 MMT semi-auto - Aygo engine management warni light on when braking - Richard Huddleston

Engine management light and warning buzzer come on when braking, even before brakes bite, and go off again when released.

All brake linings are ok, the brakes work fine and it had new fluid last November.

I'm guessing at faulty brake light switch - anyone got any other ideas?

OBD2 scanner ordered but won't be here for a few days yet.

Cheers,

Richard

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Sat 16 Jan 2016 13:13
Toyota Aygo 1.0 petrol 57 MMT semi-auto - Aygo engine management warni light on when braking - injection doc
Have you checked rear side light and brake light bulbs. A crossed filament can play havoc with EML when braking. Also check the earth for the brake lights before you start looking for more serious issues.

Does the vehicle still have the original radio fitted ?
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Sun 17 Jan 2016 11:38
Toyota Aygo 1.0 petrol 57 MMT semi-auto - Aygo engine management warni light on when braking - Richard Huddleston

Thanks. For one think I had to bodge one of the rear cluster connecting plugs a while ago after I ripped the wires out by mistake (New plug for £2? No, £900 loom from Toyota). Recently replaced both brake light bulbs as well. So I guess that's the first point of investigation.

Yes it's the original radio, why?

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Sun 17 Jan 2016 11:44
Toyota Aygo 1.0 petrol 57 MMT semi-auto - Aygo engine management warni light on when braking - Railroad.
Unlikely to be the brake switch. It only has two states, open and closed. The ECM will be able to tell whether the circuit is open or closed, and if changing between open and closed by pressing the brake pedal creates the fault then it isn't likely to be a faulty brake switch because the ECM is seeing the two different states. More likely is a short circuit which is created when the brake switch is closed.
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Sun 17 Jan 2016 19:32
Toyota Aygo 1.0 petrol 57 MMT semi-auto - Aygo engine management warning light on when braking - Richard Huddleston

Success! Thanks guys, looks like it was a loose brake light bulb. I confess last time I changed it I didn't have one of the ones with offset locating pins so I filed a normal one down. Clearly it's given up the ghost.

Still if you ask me what a ridiculous state of affairs when all the worrying "TAKE THE CAR TO A TOYOTA DEALER IMMEDIATELY" palaver comes down to a loose bulb. Bet some folk don't half get ripped off.

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Sun 17 Jan 2016 20:23
Toyota Aygo 1.0 petrol 57 MMT semi-auto - Aygo engine management warning light on when braking - injection doc
ThanK you. It's always great to have feed back, sadly very few do.
I have seen many garages falter over the most stupidest of faults.
Always best to think outside the box.

More than once have I seen automatic gearboxes replaced when a faulty bulb holder causes havoc with the gear changes or limp home mode.

Your OBD scanner won't be much good as it will only give you emission related codes
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