C121F Diagnostic Trouble Code

C121F 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 C121F diagnostic trouble code may include:

Faulty PCM
The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
Poor acceleration
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
A large air leak at or near the number one oxygen sensor would also cause a lean mixture.

Repair Processes :

Find out what kind of system you have and verify that voltage to the fuel level sensor is present at the fuel pump wiring harness. Oxygen sensors signal the engine management computer the amount of oxygen present in the exhaust, which is used in determining and controlling the fuel ratio. Look for rubbing, scraping, bare wires, worn spots or melted plastic connectors. Pull the connectors apart and carefully look at the terminals (the metal parts) inside the connectors.

Process Tips

Diagnostic trouble code C121F 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 C121F.

Fortunately, C121F is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C121F Trouble Code For Specific Cars

C121F Volvo P1900 SCP (J1850) Invalid or Missing Data for Engine Systems Other
C121F Wartburg 353 SCP (J1850) Invalid or Missing Data for Interior Lamps
C121F Dinfia Cw Hydraulic Pump Relay Circuit Range/Performance
C121F Dauer 962 HO2S Heater Control Circuit High (Bank 2 Sensor 2)
C121F Tata E 220 Mirror Passenger Up Circuit Short To Ground
C121F Mazda 2000 Transmission Transfer Case Contact Plate 'B' Short Circuit To Battery
C121F Nissan Cefiro Climate Control Temperature Differential Circuit Short To Ground