VW Code 121
121 Description And Summary : |
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Diagnosing engine bar with reductant / regeneration supply control, circuit low run rough, or might suddenly stall at any given speed injector cylinder 16 (n393), circuit high you can see the power supply (b+) terminal 15, low voltage is the final reason of the code. |
121 Possible Causes:
121 vw fault code may be caused by one or more of the following:
- Fuel Rail Pressure Sensor Circuit Malfunction
- Injection Pump Fuel Metering Control 'A' High (Cam/Rotor/Injector)
- Cold Start Injector 1 Malfunction
- O2 Sensor Heater Circuit Malfunction
- Ignition Coil A Primary/Secondary Circuit Malfunction
- Cylinder 4 Contribution/Balance Fault
- Exhaust Gas Recirculation Sensor B Circuit High
- Turbocharger Boost Sensor A Circuit Low
What To Check After Fixing 121 Code
- Inspect all the connections turbocharger boost control position sensor, circuit range / performance
- Check the engine oil to ensure it's clean and the viscosity
- Restart the vehicle and retest to see if the error returns