B0251 Mazda RX-3 Diagnostic Trouble Code

B0251 Mazda RX-3 code definition:
B0251 is a kind of OBD-II Diagnostic B-Body Diagnostic Trouble Code for Mazda RX-3.

B0251 Mazda RX-3 is described as Oxygen Sensor Circuit No Activity Detected (Bank 1, Sensor 1). This means there's a problem in the front oxygen sensor on Bank 1, as the O2 sensor is inactive. This is because the barometric pressure sensor is part of the MAF sensor. Sometimes, the MAF's sensing wire can accumulate and get covered with dirt, dust and/or oil residue, which can also lead to the error code.

Symptoms

Symptoms of a B0251 Mazda RX-3 diagnostic trouble code may include:
  • Misfire
  • Misfire
  • The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
Place of B0251 in engine

Possible Causes :

  • Fuel with a large percentage of sulfur will clog the DPF quickly
  • The Mass Airflow sensor will also cause this problem. Mass Airflow circuit malfunction.
  • An air leak forward of the DPF will change the sensor readings resulting in the code

Common Misdiagnoses

  1. Crankshaft Position Sensor Circuit Performance Problem
  2. TP Sensor Learn Not Complete Problem
  3. Low Coolant Circuit Problem
  4. Cruise Control System - Vehicle Accel Too High Problem
  5. Kick-Down Switch Failed Short Problem

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. 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. Now, clear the codes and test-drive the vehicle to see if the code is reset.

Process Tips

Diagnostic trouble code B0251 Mazda RX-3 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 B0251 Mazda RX-3.

Fortunately, B0251 Mazda RX-3 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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