C0104 Mg Va Diagnostic Trouble Code

C0104 Mg Va code definition:
C0104 is a kind of OBD-II Diagnostic C-Chassis Diagnostic Trouble Code for Mg Va.

C0104 Mg Va is described as Oxygen Sensor Circuit No Activity Detected Bank 2 Sensor 1. This code appears when the PCM (powertrain control module, also known as ECM or engine control module in other brands) remains at or close the 0.450 set voltage point. Other symptoms that may indicate this problem are when the Check Engine Light illuminates and when there is a visible lack of engine power.

Symptoms

Symptoms of a C0104 Mg Va diagnostic trouble code may include:
  • The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
  • Faulty PCM
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
  • Reduction in engine performance, especially at low RPM levels
Place of C0104 in engine

Possible Causes :

  • 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.
  • Some aftermarket accessories and performance modifications
  • An air leak forward of the DPF will change the sensor readings resulting in the code

Common Misdiagnoses

  1. Vehicle Speed Output Circuit Problem
  2. Cruise Control Servo Indicates Low Problem
  3. A/C System High Pressure High Temperature Problem
  4. PCM Stack Overrun Problem
  5. Transmission Control Module Reprogrammable Memory Problem

Repair Processes :

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. Now, clear the codes and test-drive the vehicle to see if the code is reset. 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.

Process Tips

Diagnostic trouble code C0104 Mg Va 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 C0104 Mg Va.

Fortunately, C0104 Mg Va is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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