P078C Diagnostic Trouble Code

P078C 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 P078C diagnostic trouble code may include:

Possible spark knock (detonation / pre-ignition)
Poor fuel economy
The engine oil will exhibit dilution from the ECUs attempts to increase engine temperature. Some vehicles advance the fuel injection timing slightly after top center to afterburn a small amount of fuel to increase exhaust temperatures. Some of this fuel enters the crankcase. When the ECU determines the necessity to regenerate the DPF, the service life of the oil be shortened significantly
The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.

Possible Causes :

Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.
Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.
Defective ECU strategies or components will prevent proper regeneration

Repair Processes :

Find out what kind of system you have and verify that voltage to the fuel level sensor is present at the fuel pump wiring harness. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition. 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.

Process Tips

Diagnostic trouble code P078C 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 P078C.

Fortunately, P078C is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P078C Trouble Code For Specific Cars

P078C Maserati Indy Transmission Fluid Pressure Sensor/Switch E Circuit
P078C Cottin-desgouttes 40 Fuel Shutoff Valve Control Circuit/Open
P078C Toyota Condor O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P078C Fiat Abarth LAMP DOME OUTPUT Circuit Short to Battery
P078C Tvr 420 Power Door Lock Circuit Short To Battery
P078C Mercedes Cls 350 ABS Outlet Valve Coil RF Circuit Short To Battery
P078C Matra-simca M Transmission Over Temperature Condition