Brake Fault Dash Warning

[Thingsfallapart]

I'm perplexed by a brake fault warning light. It started coming on after I replaced the brake fluid reservoir. VCDS shows no faults. I completely flushed the brake lines in this order: rear passenger, rear driver, front passenger, front driver. It appears almost every time I operate the car but not always. There is plenty of braking power and the brakes do not feel squishy.

I took the car for a drive on the highway and after about 10 miles at freeway speeds I stopped and checked the brakes. The front driver caliper was too hot to touch while all other calipers were merely warm. I pulled the front driver caliper and the piston appeared to be quite corroded around the piston boot. I replaced the caliper and car brakes fine but I still get the brake fault light.

Oddly, the brake fault light disappeared when I pulled the sensor from the brake fluid reservoir. It reappeared immediately when I reinserted the sensor.

Was the stuck piston related to the reservoir swap? A coincidence?

Why would the brake fault light go out when I pull the sensor but leave it connected to the harness?

 

[afarfalla]

IIR correctly, its telling you a light bulb is out

 

[Thingsfallapart]

Not it. All three brake lights are working.

 

[Thingsfallapart]

problem solved: the sensor was triggered by fluid level. The level was well above the minimum mark so I assumed it was faulty or some other problem. I took the screen out and fiddled with the float and it became clear it needed more fluid to prevent the sensor from activating.

As to the the caliper seizing, must have been corrosion from delayed brake flush And crud in the lines.