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OBD-II Code Mazda

P1138 — Mazda — HO2S Bank 1 Sensor 2 Signal Above 0.45V (A/F Ratio Too Rich)

The downstream oxygen sensor indicates a rich air-fuel mixture condition.

Brand Mazda
System Emissions
Severity Medium
Safe to drive? Yes, with caution
Advanced scanner Not necessarily

What does code P1138 mean on Mazda vehicles?

The downstream oxygen sensor indicates a rich air-fuel mixture condition.

Common symptoms

  • Fuel smell
  • increased emissions

Possible causes

  • Fuel system issue
  • faulty oxygen sensor

Initial recommendation

Check fuel injectors and fuel pressure, verify oxygen sensor operation.

Safety notice

This information is for guidance only. Brand-specific codes may vary by model, year, engine, transmission and vehicle configuration. It does not replace a physical inspection or diagnosis by a qualified mechanic. If the vehicle is unsafe to operate, avoid driving it and seek professional inspection.

Analyze this code with MecaOBD

Use the app to combine Mazda code P1138 with your vehicle's actual symptoms for more complete diagnostic guidance.

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