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P25A2

Brake System Control Module A Requested MIL Illumination

The primary brake system control module (ABS/ESC/iBooster) has requested the ECM to illuminate the MIL because of an emissions-relevant fault on its side — for example a regenerative braking fault on a hybrid that affects driveline torque flow. The original fault is in the brake module.

  • Check engine light: Yes
  • Emissions related: Yes
  • Repair difficulty: medium

Common causes

Ordered by how often each turns out to be the cause.

  • Internal fault in the brake module — read its DTCsCommon

Parts involved

  • Brake Control Module A

P25A2 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.