P2421 Diagnostic Trouble Code


P2421 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 P2421 diagnostic trouble code may include:
  • Lack of power
  • Faulty O2 Sensor
  • Poor acceleration
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
Place of P2421 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)
  • Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.

Repair Processes :

Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications. Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition.

Process Tips

Diagnostic trouble code P2421 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 P2421.

Fortunately, P2421 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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