P303F Diagnostic Trouble Code

P303F 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 P303F diagnostic trouble code may include:

Fuel pressure too low
Rich or lean exhaust
Diminished fuel efficiency
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)
Faulty IMRC actuator/sensor

Repair Processes :

If the scan tool has that capability, and the scan tool can operate the IMRC valves, then the problem is either resolved and a simple code clearing is all that's left or a new PCM would be called for. 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. 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 P303F 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 P303F.

Fortunately, P303F is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P303F Trouble Code For Specific Cars

P303F Vauxhall Astra Power Window RR Motor Circuit Short To Ground
P303F Osi 850 Door Unlock Disarm Switch Circuit Open
P303F Lotus Excel Traction Control Motor Circuit Short to Ground
P303F Subaru R1 LF SIDE REPEATER LAMP OUTPUT Ckt Short to Battery
P303F Abarth 600 A Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)
P303F Opel Crossland X Digital TRS Failed to Transition States in KOEO / KOER
P303F Lotus Super Traction Control of Engine Exceeds Time-Out