The heated oxygen sensor 1 (H02S-1) is an electrical source that responds
to oxygen content in the exhaust manifold. When the sensor reaches approximately
316°C (600°F), it produces a voltage based on the difference in oxygen between
the atmosphere and exhaust gas. The PCM sends a bias voltage (399-499 mV)
on the signal line, which is pulled up through high resistance. When the HO2S-1 is
cold, it produces no voltage and has extremely high internal resistance. The internal
resistance of the sensor is much greater than the resistance of the bias pull-up resistor.
However, when the sensor heats up, it produces voltage that overrides the bias voltage.
This voltage is read by the PCM to determine a rich/lean HO2S-1 signal used to adjust
injector pulse width. Under normal conditions, low sensor voltage means high oxygen
content/lean air-fuel mixture and vice versa. Normal sensor readings will fluctuate
between 10-1065 mV. DTC P0133 sets when the HO2S-1 signal rich
to lean or lean to rich average response time is too slow.
DTC Parameters
DTC P0133 will set if the average response time of the LEAN to RICH switches
is greater than 730 ms (auto), 625 ms (manual) or the average response
time of the RICH to LEAN switches is greater than 1200 ms (auto), or 975 ms
(manual):
OR
Sum of the LEAN to RICH and RICH to LEAN average response times is greater than
1200 ms (auto), 975 ms (manual) when:
| • | The condition exists for longer than 30 seconds. |
| • | The engine run time is greater than 3 minutes and 20 seconds. |
| • | The engine speed is between 2350-3000 RPM (manual) / 1800-2300 RPM
(auto). |
| • | The ECT is greater than 70°C (158°F). |
| • | The TP angle is between 22-40 percent (manual), 8-15 percent
(auto). |
| • | The loop status is closed. |
| • | The EVAP purge solenoid commanded duty cycle is greater than 80 percent. |
| • | The fuel level is greater than 10 percent. |
| • | No CKP, ECT, EVAP, fuel injector, fuel tank pressure, fuel trim, IAT,
idle speed, MAP, misfire, PCM internal fault, or TP sensor DTCs have been set. |
DTC P0133 diagnostic runs once per ignition cycle once the above
conditions have been met.
P0133 is a type B DTC.
Diagnostic Aids
Possible causes of DTC P0133:
| • | An intermittent connection or corrosion in the HO2S-1 harness connector
can set this DTC. Use the scan tool to monitor HO2S-1 voltage with the engine running
at normal operating temperature while wiggling the signal and ground wire. Make sure
the sensor is tight. |
| • | The most probable cause for DTC P0133 is contamination. Check for obvious
contamination (oil, fuel, or engine coolant) by removing the sensor. Identify and
correct the cause of the contamination if contaminated. Replace the HO2S-1. |
