P303C Diagnostic Trouble Code

P303C 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 P303C 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
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected

Possible Causes :

Fuel with a large percentage of sulfur will clog the DPF quickly
The Mass Airflow sensor will also cause this problem. Mass Airflow circuit malfunction.
Defective ECU strategies or components will prevent proper regeneration

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem.

Process Tips

Diagnostic trouble code P303C 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 P303C.

Fortunately, P303C is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P303C Trouble Code For Specific Cars

P303C Spectre R Lamp Brake Warning Output Circuit Open
P303C Innocenti J4 SCP (J1850) Invalid or Missing Data for Interior Environment
P303C Glas 1300 Over Temperature Fault
P303C Packard 300 DPFE Circuit Low Input
P303C Bristol Britannia Crankshaft Position Sensor B Circuit High Input
P303C Alfa 24 ABS Outlet Valve Coil Rear Circuit Short To Ground
P303C Mercedes-benz Vito Air Suspension Height Sensor Power Circuit Short To Ground