P004B

What it means

Boost control B mechanical/hydraulic deviation from target. Same as P0046 on actuator B. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.

Is it safe to drive?

This code can put the vehicle into limp or reduced-power mode. Avoid extended driving and have the vehicle diagnosed promptly.

Most likely causes

• Vacuum/boost line leak

  high

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

• Sensor element aged beyond calibration window

  low

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

• Sensor mounting loose - signal damping

  low

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

Related help

• Full P004B diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?