Diagnostic Instructions
DTC Descriptors
DTC P0133: HO2S Slow Response Sensor 1
DTC P0139: HO2S Slow Response Sensor 2
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
HO2S Signal
| P0131, P0137
| P0134, P0140
| P0132, P0138
| P0133, P0139
|
Low Reference
| --
| P0134, P0140
| P0132, P0138
| P0133, P0139
|
Circuit Description
The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an
Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage
within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine
the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
The HO2S utilizes the following circuits:
| • | A low reference circuit |
| • | An ignition 1 voltage circuit |
| • | A heater control circuit |
Conditions for Running the DTC
P0133
| • | The mass airflow is between 972-300 mg/tdc. |
| • | The engine speed is between 1,800-2,400 RPM. |
| • | The engine coolant temperature is greater than 70°C (158°F). |
| • | The catalytic converter temperature is between 400°C (752°F) and 900°C (1,652°F). |
| • | The fuel system is in Closed Loop. |
| • | The evaporative emissions (EVAP) purge is less than 100 percent. |
| • | The vehicle speed is between 40 km/h and 110 km/h.. |
| • | The DTC runs continuously when the above conditions are met. |
P0139
| • | The engine coolant temperature is greater than 70°C (158°F). |
| • | The catalytic converter temperature is greater than 400°C (752°F). |
| • | The fuel system is in Closed Loop. |
| • | The vehicle speed is between 5 km/h and 180 km/h. |
| • | The DTC runs continuously when the above conditions are met. |
Conditions for Setting the DTC
P0133
The ECM detects that the HO2S 1 rich-to-lean or lean-to-rich counts are greater than 65 seconds.
P0139
The ECM detects that the HO2S 2 response time is greater than 25 seconds after DTC P0420 runs.
Action Taken when the DTC Sets
DTC P0133 and P0139 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTC P0133 and P0139 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Verification
- Engine running, observe the DTC information with a scan tool. Verify that other DTCs are not set.
- Observe the DTC information with a scan tool. DTCs P0133 or P0139 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
- Verify none of the following conditions exist:
| • | Exhaust leaks near the HO2S |
| ⇒ | If you find any of the above conditions, repair as necessary. |
- If all conditions test normal, test or replace the appropriate HO2S.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
