Code result
P257B
Vacuum Reservoir Control Circuit Low
Moderate severity
What it means
The vacuum reservoir control circuit reads stuck low — short to ground or low-side driver stuck on. The actuator may be energised continuously when it should be off.
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
Control wire shorted to ground
highOne of the most commonly reported causes for this code — check this first.
Connector pins corroded - high contact resistance
lowLess common, but worth ruling out after the more likely causes.
Harness chafing through insulation
lowLess common, but worth ruling out after the more likely causes.
Related help
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