C120A Diagnostic Trouble Code

C120A is a kind of OBD-II Diagnostic C-Chassis 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 C120A diagnostic trouble code may include:

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
Faulty or damaged wiring
Hesitation upon acceleration
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)
Defective ECU strategies or components will prevent proper regeneration

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.

Process Tips

Diagnostic trouble code C120A 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 C120A.

Fortunately, C120A is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C120A Trouble Code For Specific Cars

C120A Nash 400 Catalyst System Efficiency Below Threshold (Bank 1)
C120A Allard Palm Beach Air Bag Driver Inflator Circuit Resistance Low on Squib
C120A Mitsubishi Toppo B+ Supply To VCRM Fan Circuit Malfunction
C120A Alma Six Air Bag Memory Clear Circuit Open
C120A Wolseley 14 SCP (J1850) Invalid or Missing Data for Seat Switches
C120A Honda S500 Rear Wiper Select Switch "D" Short to Ground
C120A Hyundai Hcd