P1051 - FAULT CODE - OBD2

POST UPDATED IN February, 2023

P1051 Code failures by brands

P1051 INFINITI, NISSAN: AIR FUEL RATIO SENSOR 1 HEATER CONTROL CIRCUIT LOW BANK 2

Description of DTC code P1051

The fuel injection system of vehicles is based on conventional oxygen sensors. However, in the last few years, these sensors have given way to Air Fuel Ratio sensors (A/F), which offer higher accuracy.

An A/F sensor, also known as a “lambda sensor”, is installed in the exhaust manifold or the front exhaust pipe upstream of the catalytic converter. Its purpose is to measure the oxygen content of the exhaust over a wider range. Although similar in appearance to a conventional Oxygen Sensor, these sensors have more wires. The information collected by the Air-Fuel Ratio Sensor is sent to the ECM as a feedback signal, which will accordingly adjust the air-fuel ratio to keep it within its optimum level.

When the P1051 OBDII fault code is set, it is because after performing the ON/OFF service check of the Air-Fuel Ratio Sensor 1 heater, the current amperage was found to be out of range, resulting in an excessively low voltage signal being sent to the Engine Control Module.

Symptoms of fault code P1051

  • Check Engine Lamp on.
  • Unstable idle speed.
  • Increased fuel consumption.

Causes of OBD2 P1051

The reasons for setting the P1051 OBD2 diagnostic code are:

  • The Air/Fuel Ratio Sensor 1 circuit could have damage to its wiring or connectors.
  • The A/F Sensor 1 electrical connections could be faulty causing the low voltage condition.
  • The Air Fuel Ratio Sensor 1 on bank 2 could be faulty.

Possible solutions of the DTC code P1051

The steps to troubleshoot the DTC P1051 OBDII code are as follows:

  • As a first step consult the Technical Service Bulletins.
  • Inspect the A/F Sensor 1 wiring from bank 2 and check for common damage. Repair it as necessary.
  • Following the steps outlined by the manufacturer, perform electrical checks on the Air-Fuel Ratio Sensor. If you discover a parameter outside the manufacturer's specifications, make the appropriate corrections.
  • Measure the resistance of the Air-Fuel Ratio Sensor, if this value does not match the specified value, replace it.

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