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Diagnose/P0478
P0478Medium SeverityEngine

Exhaust Pressure Sensor B Circuit Low Input

What This Means

The exhaust pressure sensor B voltage is below the minimum expected threshold. This sensor monitors exhaust back-pressure which is important for turbo control and DPF regeneration on diesel engines.

Common Symptoms

  • Check engine light on
  • Reduced power
  • Poor turbo response
  • DPF regeneration issues

Common Causes

  • Faulty exhaust pressure sensor
  • Clogged sensor port
  • Wiring damage
  • Exhaust system restriction
  • DPF issue

Estimated Repair Cost

$150 – $600
Parts and labor (varies by vehicle and location)
Difficulty:Moderate

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For informational purposes only. Diagnostic trouble codes are starting points for diagnosis, not definitive answers. Always consult a certified mechanic for proper diagnosis and repair. Estimated costs vary by vehicle, location, and shop rates.