Along with the check engine light turning on, OBD II trouble code(s) are stored in the engine control computer. Using a trouble code scan tool these code(s) can be retrieved from your Jeep Liberty's ECU. The trouble code(s) will indicate the emission component responsible for turning on the check engine light. You may then further diagnose the fault.
If you see that the new trouble code(s) once again indicate a problem with the catalytic converter and/or the oxygen sensor(s), ensure you replaced the correct oxygen sensor, ensure the wiring and harness of the oxygen sensor is in good shape, and connected firmly. We also recommend paying close attention to the type of CAT or O2 trouble code. Does the trouble code indicate an absolute fault with the component or does it show a lazy O2 sensor or CAT efficiency low. With either of these two trouble codes (/P0132/P0133 and P0430/P0420) the problem can be related to air/fuel mixture. Look for problems which might be causing your Jeep Liberty to run rich or lean, and not necessarily a problem with either the oxygen sensor or Catalytic Converter. The OBD II trouble codes mentioned above are always misleading.
