P0146
Circuit Description
The PCM provides a 0.45 volt reference to the oxygen sensor on CKT 1668. When the Oxygen Sensor reaches operating temperature it will generate a counter voltage that will vary based on the amount of oxygen in the exhaust. The post-converter heated oxygen sensor is located in the exhaust after the catalytic converter. A lean exhaust will generate a low voltage and cause the 0.45 reference to move lower. A rich exhaust will generate a high voltage and cause the 0.45 reference to move higher. If the oxygen sensor cannot respond under the test conditions and generate a voltage greater than 0.609 volt or less than 0.307 volt, it will set a DTC P0146. Possible causes of DTC P0146 are:
^ Open in CKT 1668 or 1669.
^ Short to voltage on CKT 1668 or 1669.
^ Oxygen sensor that malfunctions.
^ An ineffective oxygen sensor heater.
Conditions for Setting the DTC
Test Conditions
^ DTCs P0117, P0118, P0122 and P0123 not set.
^ Coolant temperature 75°C (167°F) or greater.
^ Throttle between 2.2 and 81.6 degrees.
^ (Calculated) Throttle position switch open.
^ Engine speed 800 RPM or greater.
Failure Condition
Oxygen sensor voltage stays between 0.307 volt and 0.609 volt for 250 out of 300 seconds (oxygen sensor voltage not toggling).
Action Taken When the DTC Sets
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive drive trips that the diagnostic runs and fails.
^ The PCM will record operating conditions at the time the DTC sets. This information will be stored in the Freeze Frame and Failure Records.
^ A first failure of this DTC will store in Last Test Failed but not History.
Conditions for Clearing the MIL/DTC
^ The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
^ A Last Test Failed DTC will clear when the diagnostic runs and does not fail.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any diagnostic test.
^ PCM battery voltage is interrupted.
^ Using a Scan tool.
Diagnostic Aids
Notice: Never solder heated oxygen sensor wires. For proper wire and connection repair, refer to Section 8.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
3. Measuring voltage with a voltmeter will isolate a sensor problem from a PCM wiring problem.