P1273 - FAULT CODE - OBD2

P1273 NISSAN - AIR FUEL RATIO SENSOR SENSOR 1 BANK 1 LEAN MIXTURE

The Air/fuel ratio sensors measure the oxygen in the exhaust gas. Unlike the oxygen sensors that have a signal variation between 0.9 and 0.3V, depending on whether the mixture is lean or rich, the air/fuel ratio sensors give the exact oxygen content to the exhaust stream. Then, they generate a signal that matches exactly that value.

The Air Fuel Ratio Sensor makes the signal current flows in two directions, which are positive and negative. The PCM (Powertrain Control Module) supplies these sensors with 2.6 volts of reference. In some cases, it supplies 3.3V, which works as a power source. As the air/fuel mixture changes during normal engine operation, the signal voltage sent tends to shift to the positive direction if the mixture is lean. When the mixture is richer, it shifts in the negative direction.

However, when the sensor is working properly and the engine or exhaust system is not faulty, current flow is completely stopped as long as the exhaust gas composition is “stoichiometric”. This means that all of the fuel being burned uses all of the available air in the air/fuel mixture. If the PCM detects a lean operating condition or too much air in the mixture, the P1273 OBDII diagnostic code will be set.

• Check Engine light ON.
• General engine failures.
• Instabilities at idle.

Reasons for setting the P1273 OBD2 DTC code on a Nissan vehicle:

• There may be damage to the wires or connectors in the air-fuel ratio sensor
• The air-fuel ratio sensor number one on bank 2 may be bad.
• A fuel injector could be faulty.
• Fuel pressure may not be enough.
• The airflow meter may be damaged.

Steps to solve the P1273 OBDII fault code on Nissan vehicles:

• Consult the TSB (Technical Service Bulletins).
• Scan the vehicle to check for other stored trouble codes, especially those related to the fuel system. If so, diagnose those codes first.
• Perform a visual inspection of the cables and connectors leading to the Air-Fuel Ratio Sensor. If you discover damage such as burns, corrosion, or wear on these components, make repairs.
• Check the condition of the fuel injectors. If one of the injectors is damaged, the fuel pressure will be directly affected. Repair as necessary.
• Follow the manufacturer's recommendations to check the condition of the Air-Fuel Ratio Sensor. Measure the resistance and continuity values of the wiring harness. If you determine that it is defective, replace it.