U0438

What it means

The Park Brake Control Module is present on the data bus but the values it reports are implausible — out of range, frozen, or failing the checksum or rolling-count check. The receiving modules reject the data. Electronic parking-brake operation may be limited. Causes include a faulty sensor feeding the module, internal computation errors, a software or calibration mismatch after a repair, or bus interference corrupting the frames.

Is it safe to drive?

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

• EPB actuator/motor marginal

  high

  One of the most commonly reported causes for this code — check this first.

• EPB internal computation fault

  medium

  A plausible cause — test and verify before replacing parts.

• Gateway module routing CAN messages incorrectly

  low

  Less common, but worth ruling out after the more likely causes.

Related help

• Full U0438 diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?