P1152 — Mazda — HO2S Bank 2 Sensor 1 Signal Above 0.45v AF Ratio Too Rich

P1152 (Mazda): HO2S Bank 2 Sensor 1 Signal Above 0.45v AF Ratio Too Rich — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

HO2S Bank 2 Sensor 1 Signal Above 0.45v AF Ratio Too Rich. Source catalogue definition; confirm applicability using vehicle service information.

Affected system: Powertrain

Symptoms

  • Check Engine light illuminated
  • Increased fuel consumption
  • Rough engine idle
  • Black smoke from the exhaust
  • Engine hesitation during acceleration

Possible causes

  • Faulty Bank 2 Sensor 1 Oxygen sensor
  • Leaking fuel injectors
  • Excessive fuel pressure
  • Faulty Mass Air Flow (MAF) sensor
  • Exhaust leaks upstream of the sensor

What to check

  • Inspect the O2 sensor wiring for shorts or damaged insulation
  • Measure fuel pressure to ensure it is within manufacturer specifications
  • Monitor live data for the Bank 2 Sensor 1 voltage using a diagnostic scan tool
  • Check the fuel injectors for proper pulse and potential leakage
  • Test the MAF sensor signal output at various engine loads
  • Perform a smoke test to identify exhaust leaks near the sensor