P0C78 Diagnostic Trouble Code

P0C78 is a kind of OBD-II Diagnostic P-Powertrain 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 P0C78 diagnostic trouble code may include:

The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
Faulty PCM
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
Diminished fuel efficiency

Possible Causes :

The Mass Airflow sensor is a hot wire that senses the volume of air entering the intake manifold. The computer uses this information to control fuel mixture.
Defective ECU strategies or components will prevent proper regeneration
An air leak forward of the DPF will change the sensor readings resulting in the code

Repair Processes :

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. With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. Once located, visually inspect the connectors and wiring. Look for rubbing, scraping, bare wires, worn spots or melted plastic connectors.

Process Tips

Diagnostic trouble code P0C78 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 P0C78.

Fortunately, P0C78 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P0C78 Trouble Code For Specific Cars

P0C78 Holden Vl PRC Solenoid Circuit Malfunction
P0C78 Volkswagen Up
P0C78 Citroen C3 Iii Front Wiper Select Switch "C" Short to Ground
P0C78 Maserati 4200 Gt Transmission Fluid Pressure
P0C78 Buick Rendezvous Cylinder Head Temp Sensor High Input
P0C78 Jowett Javelin Seat Headrest Feedback Potentiometer Circuit Short to Battery
P0C78 Citroen 7a Flash To Pass Switch Circuit Short To Battery