Engine-Codes - Generic - P1278

P1278 Code - Air Fuel Ratio Sensor 1 Bank 1 Circuit Slow Response

- Code Popularity: 42,765 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 2/3
Table of contents
ChatAC AutoCodes.com AI Chat

What are the Possible Causes of the DTC P1278?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Air fuel ratio (A/F) Sensor 1 Bank 1
  • Air fuel ratio (A/F) Sensor 1 Bank 1 Harness or connectors is 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 PVC
  • Faulty Air Flow Meter
⚠ Does your Car have Safety Recalls? → Check here

How to Fix the DTC P1278?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Search for P1278 Questions and Answers: Search here →

What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P1278 code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

What Does the P1278 Code Mean?

The A/F sensor is a planar dual-cell limit current sensor. The sensor element of the A/F sensor is the combination of a Nernst concentration cell (sensor cell) with an oxygen-pump cell, which transports ions. It has a heater in the element.
The sensor is capable of precise measurement λ= 1, but also in the lean and rich range. Together with its control electronics, the sensor outputs a clear, continuous signal throughout a wide λ range (0.7 < λ < air).
The exhaust gas components diffuse through the diffusion gap at the electrode of the oxygen pump and Nernst concentration cell, where they are brought to thermodynamic balance.
An electronic circuit controls the pump current through the oxygen-pump cell so that the composition of the exhaust gas in the diffusion gap remains constant at λ = 1. Therefore, the A/F sensor is able to indicate air/fuel ratio by this pumping of current. In addition, a heater is integrated in the sensor to ensure the required operating temperature of 700 - 800 C (1,292 - 1,472 F).

P1278 Code - Air Fuel Ratio Sensor 1 Bank 1 Circuit Slow Response

Need more Information on the Code?

Need more information on how to fix the P1278 code? Get Access to Factory Service Manuals

Code P1278 Information for Specific Makes

Need Help with the Code?

Get the P1278 code diagnosed by a professional: Find a repair shop in your area