Home › Fault Codes › Cars & OBD › Standard › P0136
P0136

O2 sensor circuit (Bank 1 Sensor 2)

The ECU has detected a malfunction in the downstream oxygen-sensor circuit on Bank 1.

What this code means

The ECU has detected a malfunction in the downstream oxygen-sensor circuit on Bank 1.

Possible causes

  • Failed downstream oxygen sensor
  • Wiring or connector fault
  • Exhaust leak
  • Catalyst or mixture issue affecting sensor readings

Common symptoms

  • Check engine light
  • Often little change in driveability
  • Possible emissions-test failure

Checks to make

  1. Inspect downstream sensor wiring
  2. Check for exhaust leaks
  3. Review sensor voltage/activity
  4. Check for catalyst and fuel-mixture codes

Safety

  • Do not replace parts from the code alone. Confirm the fault with live data, wiring checks and manufacturer procedures. Keep clear of hot or moving engine components.

Model notes

The code definition is generic; exact diagnostic thresholds, component locations and repair procedures vary by vehicle.