P249B Diagnostic Trouble Code


P249B 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 P249B diagnostic trouble code may include:
  • Poor acceleration
  • Cherry red hot catalytic converter
  • Possible spark knock (detonation / pre-ignition)
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
Place of P249B in engine

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)
  • 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.

Repair Processes :

If you find a related TSB, the information will often help in diagnosing the code in question as TSBs are crested from many thousands of repairs. 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 P249B 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 P249B.

Fortunately, P249B is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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