P2A00 – O2 Sensor Circuit Range/Performance Bank 1 Sensor 1

Meaning:

When the upstream O2 sensor circuit has failed to cycle as expected by the PCM, the P2A00 happens
The P2A00 is triggered when the upstream O2 sensor circuit has failed to cycle as expected by the PCM

The upstream O2 sensor circuit has failed to cycle as expected by the PCM over a period of time predetermined by the PCM.

Main Symptoms:

Possible Causes:

  • Defective O2 sensor 1 in bank 1
  • Burnt, open, broken, shorted or disconnected wire/connector in the sensor circuit
  • Vacuum leak
  • Defective MAF sensor
  • Leak in engine exhaust

Diagnostic Steps:

  • Visually inspect all wiring harnesses to O2 sensor circuits, especially sensor 1 of bank 1
  • Check for leaks in engine and vacuum system
  • Address other codes, reset all codes and do test drive. If the code returns check resistance of MAF sensor and O2 sensor. Replace as necessary

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