P120B Diagnostic Trouble Code

P120B 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 P120B 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
Rich or lean exhaust

Possible Causes :

The Mass Airflow sensor will also cause this problem. Mass Airflow circuit malfunction.
Fuel with a large percentage of sulfur will clog the DPF quickly
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. Pack the connector cavity with dielectric silicone compound (same stuff they use for light bulb sockets and spark plug wires) and reassemble.

Process Tips

Diagnostic trouble code P120B 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 P120B.

Fortunately, P120B is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P120B Trouble Code For Specific Cars

P120B Alvis Td Air Suspension Disable Switch Circuit Open
P120B Case Jic Door Ajar Lamp Circuit Failure
P120B Mercedes R 350 Accessory Delay Relay Coil Circuit Open
P120B Benz 37 Boost Calibration High
P120B Rover 220 IDM Input Circuit Malfunction/ Ignition Coil Control Circuit High Voltage
P120B Volkswagen Phaeton Right Tail Lamp Circuit Failure
P120B Innocenti 650 SCP (J1850) Invalid or Missing Data for Function Read Engine Torque