P1051 - FAULT CODE - OBD2

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

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.

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

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.

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.