Primary
The Heated Oxygen Sensor (HO2S) detects the oxygen content in the exhaust gas and signals the ECM. In operation, the ECM receives the signals from the sensor and varies the duration during which fuel is injected. To stabilize the sensor's output, the sensor has an internal heater.
^ Primary HO2S (Sensor 1) is installed in the exhaust pipe A.
^ Secondary HO2S (Sensor 2) is in the TWC.
[P0131] The scan tool indicates Diagnostic Trouble Code (DTC) PO131: A low voltage problem in the Primary Heated Oxygen Sensor (Primary HO2S) (Sensor 1) circuit.
[P0132] The scan tool indicates Diagnostic Trouble Code (DTC) PO132: A high voltage problem in the Primary Heated Oxygen Sensor (Primary HO2S) (Sensor 1) circuit.
[P0133] The scan tool indicates Diagnostic Trouble Code (DTC) PO133: A slow response problem in the Primary Heated Oxygen Sensor (Primary HO2S) (Sensor 1) circuit.
Description
By controlling the air/fuel ratio with a primary HO2S (Sensor 1) and a secondary HO2S (Sensor 2), the deterioration of the primary HO2S (Sensor 1) can be evaluated by its feedback period. When the feedback period of the primary HO2S exceeds a certain value during stable driving conditions, the sensor will be judged as deteriorated.
When deterioration has been detected during two consecutive trips, the MIL comes on and DTC PO133 will be stored.
NOTE:
^ If DTC P0131, P0132 and/or P0135 are stored at the same time as DTC P0133, troubleshoot those DTCs first, then troubleshoot DTC P0133.
Possible Cause:
^ Primary HO2S (Sensor 1) Deterioration
^ Primary HO2S Heater (Sensor 1) Deterioration
^ Exhaust system leakage