P1278 NISSAN Possible Causes
- Faulty Air/Fuel Ratio (A/F) Sensor 1 Bank 1
- Air/Fuel Ratio (A/F) Sensor 1 Bank 1 wiring harness or connectors open or shorted
- Air/Fuel Ratio (A/F) Sensor 1 Bank 1 circuit poor electrical connection
- Fuel pressure
- Faulty fuel injector
- Intake air leaks
- Exhaust gas leaks
- Faulty PCV
- Faulty mass air flow meter
How is P1278 NISSAN code repair performed?
Start by checking the “Possible Causes” listed above. Visually inspect the associated wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
When is the code detected?
The response (from RICH to LEAN) of the A/F signal calculated by the ECM from A/F Sensor 1 signal takes longer than the specified time.
Possible Symptoms
- Engine light on (or service engine soon warning light)
- Possible rough engine idle
P1278 NISSAN Meaning
The A/F sensor is a planar dual-cell limit current sensor. The sensor element of the A/F sensor combines a Nernst concentration cell (sensor cell) with an oxygen pump cell, which transports ions. It contains a heating element within the element.
The sensor can accurately measure λ=1, as well as in both lean and rich ranges. With its control electronics, the sensor provides a clear and continuous signal across a wide λ range (0.7 < λ < air).
Exhaust gas components diffuse through the diffusion gap at the oxygen pump electrode and Nernst concentration cell, where they reach thermodynamic equilibrium.
An electronic circuit controls the pump current through the oxygen pump cell so that the exhaust gas composition in the diffusion gap remains constant at λ=1. Therefore, the A/F sensor can indicate the air/fuel ratio through this pumping current. Additionally, a heating element is integrated into the sensor to maintain the required operating temperature of 700 to 800°C (1,292 to 1,472°F).