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The mkiv Supra Owners Club

Flickering/intermittent red warning light

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Flickering red warning light


Also known as:

Intermittent red warning light

The red triangle light on the dash keeps coming on and going off while I'm driving


What is it?

This red warning light lights up when any problems are detected by the ECU. Sometimes another light will light up at the same time. In fact, even putting the handbrake on lights it up. Sometimes, though, it'll appear to flicker or it'll come on when you brake then go off when you accelerate.


Usually caused by:

Low brake fluid. Yes, your brake fluid may look like it's full or even above the Max line on the reservoir, but I promise, if you've got intermittent red light syndrome, it needs topping up a bit.



The fluid gets lower because your brake pads are wearing and the caliper pistons stick out further and further as the pads get thinner and thinner. This means brake fluid slowly leaves the reservoir to take up the slack cause by the pistons being further out, and eventually the fluid gets to the point where it sits right on the edge of the sensor. The flickering is caused by the fluid being just below the sensor when subjected to g forces, eg braking, cornering etc..


How bad is this problem?

Not overly bad. If the red light stays on all the time, you've got low fluid and need to get it topped up. If the fluid level keeps falling that's even worse as you've got a leak. But when it's flickering, your brakes aren't about to fail :)


Other possible causes:

A solid red light usually means something more major has gone wrong. See checking for diagnostic codes for a way to diagnose what's up.



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  • 9 months later...
Guest jonnybsupra1

My red warning light comes on at high(ish) speed.

Noticed the 'door open' light flashing at the same time and found it is actually the switch under the bonnet. As the car goes faster, the bonnet lifts slightly and the switch swiches the light on.

Just needs a slight adjustment.


I'm sure there are many other reasons why this warning light would come on.

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Yes the damn light will come on under other circumstances but it's the *flickering* action that is important here. I've had the lifting bonnet one as well, but believe me, if you do a search for this problem on the board, you'll find every time it's low brake fluid. Which makes it, in my book, a frequently asked question :p


And you don't get error codes just by hitting the speed limiter - a code 42 means the ECU has lost contact with the sensor entirely. The act of fitting a different delimiter can cause the fault in the wiring to be cured...



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