P301B Diagnostic Trouble Code

P301B 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 P301B diagnostic trouble code may include:

Poor acceleration
Cherry red hot catalytic converter
Possible spark knock (detonation / pre-ignition)
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)
A faulty oxygen sensor. This will set a code in itself, however, a faulty oxygen sensor does not automatically condemn the sensor. The code just means that the sensor signal was not within specifications. An air leak or any of the above will cause an erroneous signal. There is a multitude of O2 codes relating to O2 performance which gives a clue to the problematic area.

Repair Processes :

It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem. 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. Look at the plug wires to make sure they are not burnt or laying on the exhaust.

Process Tips

Diagnostic trouble code P301B 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 P301B.

Fortunately, P301B is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P301B Trouble Code For Specific Cars

P301B Skoda 1201 Key Line Voltage
P301B Mazda Demio 2 Transmission Transfer Case Shift Motor Short Circuit To Battery
P301B Mg Midget Air Suspension Vent Solenoid Output Circuit Short To Ground
P301B Gmc Acadia Park / Neutral Switch Input Circuit Low
P301B Daihatsu U4b GPS Receiver Error
P301B Nissan Ideo Clutch Switch Input Circuit Malfunction
P301B Eagle Summit Incorrect Gear Ratio