C0278 Diagnostic Trouble Code

C0278 is a kind of OBD-II Diagnostic C-Chassis Diagnostic Trouble Code.

It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.

Symptoms

Symptoms of a C0278 diagnostic trouble code may include:

Engine surge
Blown fuse (if applicable)
Lack of power
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected

Possible Causes :

A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
Faulty IMRC actuator relay (if equipped)
Rarely - faulty Powertrain Control Module (PCM-programming required after replacement)

Repair Processes :

If you find a related TSB, the information will often help in diagnosing the code in question as TSBs are crested from many thousands of repairs. Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.

Process Tips

Diagnostic trouble code C0278 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before C0278.

Fortunately, C0278 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C0278 Trouble Code For Specific Cars

C0278 Ford Territory Mirror Passenger Vertical Switch Circuit Open
C0278 Chevrolet Alero Driver Door Ajar Circuit Failure
C0278 Armstrong Siddeley Whitley Air Suspension Rear Height Sensor Low Signal Circuit Open
C0278 Skoda Rapid Lack Of HO2S Switch - Adaptive Fuel At Limit
C0278 Chevrolet Sonic Electric Air Pump Primary Failure
C0278 Ford Cortina Main Blower Motor Relay Circuit Short to Battery
C0278 Lincoln Mark Lt Throttle position sensor intermittent