Recently, my Evo X had a red warning text lit up on the dashboard for Christmas. Occasionally, it would say "Brake system service required" when I was accelerating as well as when I was braking. I checked the brake fluid and the level was normal. There were no diagnostic trouble codes (DTCs) in the ECU.

I had also noticed that, in the past few weeks, the car was making a barely audible metallic scraping noise from the front calipers. The scraping noise could be undoubtedly heard if I rolled down the window and drove at a walking pace.

Remedy

So I brought the Evo X to a local mechanic (who frequently works on Ralliarts and WRX's). He inspected the Brembo caliper pins and pistons and found the lubricant was almost gone. The front left caliper was almost seized. The front right caliper was also sticking. Thus, he cleaned all four disc brake calipers, and lubricated them with silicone moly brake lubricant, and asked me to drive the car for a week or so to see if the red warning comes back.

Postscript

After paying for the brake service, I have been driving the Evo X for 2 weeks. The brake pedal feels great. It's now smooth and more linear. The "Brake system service required" has never come back. I'm quite happy that it's simple problem that the brake caliper seized, rather than the dreaded CMC leaking or bad brake fluid level sensor.