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Diagnose/P0042
P0042Low SeverityEmissions

HO2S Heater Control Circuit (Bank 1, Sensor 3)

What This Means

The heater control circuit for the third oxygen sensor position on bank 1 has malfunctioned. Some vehicles with multiple catalytic converters use a third sensor.

Common Symptoms

  • Check engine light on
  • No drivability issues
  • Slightly higher emissions
  • May fail emissions test

Common Causes

  • Failed heater element
  • Blown fuse
  • Wiring damage
  • Corroded connector
  • PCM driver fault

Estimated Repair Cost

$100 – $400
Parts and labor (varies by vehicle and location)
Difficulty:Easy

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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.