YC - Red Brake Warning Light (!)

[YarisHybrid2016]

Hi,

Aside from the usual cold temperature/sensor-frozen-over annoyances, there was one stand-out light that was not expected: the RED brake warning light.

According to the manual, this is for the sensor for brake fluid level or "brake system malfunction" (brake fluid was checked only a few days ago and full; checked again and no change - still full). Brakes seem to operate normally, and no signs of anything abnormal.

Car was sat overnight in -5 deg. C conditions. Driven to work this morning. Wife reported it came on about 10 minutes after leaving, and was on for about 5 minutes before it went off again. She was driving (not braking) at the time it illuminated.

Appears to possibly be a bad sensor, but just wondering if there could be more to it?

Car has 14k miles on it, and has only had one service since it was purchased last year (car is about 18 months old).

I did wonder if there may be water in the brake fluid, but I'd be concerned if there was enough to trigger the sensor this way.

Going to get it into the garage anyway and see if any fault codes are stored. Better safe than sorry, as it is unknown how and what systems such a light might affect even if it is only a bad sensor and not an actual problem.

As an aside, my car had a spurious speed reading while parked on the drive. Speedo went from zero to 1 MPH and back to zero again while stationary and in PARK. Also sub-zero conditions, and the car was covered in frost.

I hope the Gen. 4 doesn't have many gremlins hiding in its electronics. Two cars, both with spurious issues in cold weather isn't a great sign.

[TonyHSD]

Hm , 

interesting. Red warning brake light is strange if only on its own and can indicate a couple of things indeed. If it’s a brake system malfunction as a result of speed sensor issues there will be yellow warning ⚠️ lights and engine management light too, regenerative braking loss as well. The car hybrid system to work as usual need all 4 wheels correct speeds. 
Not sure in your case could be anything from low voltage 12v Battery, water inside the sensor wire harness, or something similar or completely different. 
Parking brake issues more likely to set red light only and low level brake fluid. 
Scan the codes and monitor for warning if they come back. 

[Cyker]

What is this red brake warning light? Can you grab a picture if it happens again...?

I'm assuming you don't mean the red car-thinks-you're-about-to-crash warning...?

[YarisHybrid2016]

Hi,

@Cyker

This one. On the YC it appears inside the water temperature gauge.

[anchorman]

Doesn’t that double as the handbrake warning light?  It might not be cold related but if it is, I’d check both the fluid and the handbrake (has come right off).  Depending on pad wear you don’t want it brimming full or you’ll end up getting it out again when you fit new pads unless it’s due a fluid change at the same time.  

[TonyHSD]

17 hours ago, YarisHybrid2016 said:

Hi,

@Cyker

This one. On the YC it appears inside the water temperature gauge.

Parking brake when engaged this light illuminates too, perhaps if the callipers been frozen and not released the pads correctly. After that the ice has probably melted and all back to normal. If the car has issues with brake booster , ABS, pumps, speed sensors will trigger also yellow warning ⚠️. 

[YarisHybrid2016]

If it was parking brake related, wouldn't the (P) symbol also be displayed if it hadn't fully released? That's not to say it couldn't cause this problem though.

[YarisHybrid2016]

On 12/4/2023 at 8:07 AM, anchorman said:

Doesn’t that double as the handbrake warning light?  It might not be cold related but if it is, I’d check both the fluid and the handbrake (has come right off).  Depending on pad wear you don’t want it brimming full or you’ll end up getting it out again when you fit new pads unless it’s due a fluid change at the same time.  

Fluid is checked regularly anyway, and it is sat at the full mark. Good point regarding the handbrake. No way to check it and I wasn't in the car at the time of the fault. Exercising the EPB could be an idea, and next time releasing the parking brake when leaving it overnight might be an idea (it actually says to do this in the manual and has a procedure).

It's been a week or so since it happened, and there hasn't been a recurrence, so hopefully it was something like ice rather than anything else. Car booked in for next week so will update.