Code result
P25C9
Brake System Control Module B Requested MIL Illumination
Moderate severity
What it means
A second brake system control module (typically the redundant secondary unit on by-wire or AV-grade brake systems) has signalled an emissions-relevant fault and requested the engine controller to switch on the MIL.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Active DTC stored in the secondary brake module
highOne of the most commonly reported causes for this code — check this first.
Communication loss interpreted as MIL request
lowLess common, but worth ruling out after the more likely causes.
Related help
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