How to Troubleshoot Check Engine for a Ford Ranger 2.3L


The check engine light on a Ford Ranger with the 2.3-liter engine shows that an irregularity or failure has occurred somewhere in the computer controlled engine management circuit. The computer indicates that a code has been set, identifies the affected circuit or device, and illuminates the check engine light. The light will not indicate any problem with the mechanical aspects of the engine, such as oil pressure, water temperature or alternator output. You can check the computer code by using a code scanner, which you can buy at an auto parts store.

Things You'll Need

  • Code scanner
  • Pencil and paper
  • Connect the code scanner cable to the OBD 11 port on the left side of the steering column and under the dash.

  • Turn the ignition key to the "On" position with the engine off. Press the "Read" key on the code scanner. The scanner will begin to interrogate the computer and display the codes stored in the computer. The codes are always a letter followed by four numbers. The letter designates the subsystem and the number relates to the specific problem. Write the code(s) down.

  • Cross-reference the codes with the code sheet provided with the code scanner. In this way, you can identify the fault.

  • Repair the problem indicated by the code and further diagnosis. Remember that stand-alone items such as airflow sensors or throttle position sensors are most likely bad as long as they have a good connection. Check their electrical connections before replacing them. Other items, such as the oxygen sensor, are not as easily diagnosed.

  • Turn the key to the "On" position again and press the "Erase" key on the code scanner. This will reset the computer and turn off the check engine light. Keep a record of the codes, in case the problem repeats itself.

Tips & Warnings

  • The oxygen sensor senses the amount of free oxygen in the exhaust system, allowing the computer to read the mixture, whether rich or lean. The computer sets a code if the fuel mixture becomes irregular and uncontrollable and the computer has to vary the mixture and timing to compensate. This however, does not mean the sensor is bad, but just displaying a reading outside of normal parameters.
  • Different things can cause this; a bad spark plug will not burn the fuel completely, making the mixture rich. A bad plug wire, faulty timing, a bad coil, a dirty fuel injector, a stuck valve, a leaking intake manifold, a stuck EGR valve or a loose vacuum line can all also cause a lean or rich mixture.
  • All these items must be checked before condemning the sensor. The check engine light cannot be turned off and the computer reset unless the original problem has been corrected.

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