P2278 Fault Code

O2 Sensor Signals Swapped Bank 1 Sensor 3/Bank 2 Sensor 3

• What does that mean?
• Symptoms
• Causes
• Solutions

The P2278 fault code indicates a problem with the oxygen sensor signals being swapped between Bank 1 Sensor 3 and Bank 2 Sensor 3. The oxygen sensors are crucial components for monitoring exhaust gas and ensuring optimal engine performance and emissions control. When the signals from these sensors are incorrectly interpreted, it can lead to poor engine performance, increased emissions, and potential damage to the engine over time. This code often triggers the check engine light, indicating the need for diagnostics.

What are the symptoms of the P2278 code?

Common symptoms associated with the P2278 fault code may include:

• Illuminated check engine light on the dashboard.
• Decreased fuel efficiency as the engine struggles to maintain optimal performance.
• Rough idling or stalling due to improper air-fuel mixture.
• Increased emissions that may fail an emissions test.
• Changes in engine performance, such as hesitation or lack of power.

What causes the P2278 code?

Potential causes of the P2278 fault code may include:

• Faulty oxygen sensors that are malfunctioning or damaged.
• Wiring issues, such as damaged or corroded connections between the sensors and the Engine Control Module (ECM).
• Faulty ECM that misinterprets sensor signals.
• Incorrect installation of oxygen sensors after replacement or repair.
• Exhaust leaks that affect sensor readings.

How to fix P2278?

To address the P2278 fault code, follow these steps:

• Inspect and test Bank 1 Sensor 3 and Bank 2 Sensor 3 for proper functionality; replace any faulty sensors.
• Check the wiring and connectors for damage or corrosion; repair or replace as necessary.
• Ensure that the sensors are correctly installed and positioned.
• Use a scan tool to clear the fault code and test drive the vehicle to see if the code returns. If it does, further investigation of the ECM may be required.