Circuit Description
The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity. The PCM counts the number of times that the a rich to lean and lean to rich response is indicated and adds the amount of time it took to complete all the transitions. The PCM uses this information in order to determine an average time for each transition. A DTC P0133 will set if the average transition (response) time is too slow.
A lean to rich transition is indicated when the HO2S voltage changes from less than 300 mV to greater than 600 mV. A rich to lean transition is indicated when the HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly is likely to be faulty and should be replaced.
Conditions for Running the DTC
| • | Barometric pressure is greater than 75 kPa. |
| • | Engine coolant temperature is greater than 80°C (176°F). |
| • | Intake air temperature is between -10°C to 70°C (14°F to 158°F). |
| • | Vehicle speed is above 50 km/h (30 mph) for 2 minutes and then idled for 2 minutes. |
Conditions for Setting the DTC
| • | The response rate average is greater than 1 second. |
| • | The switch cycle average is greater than 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutively passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
If any DTCs other than Fuel Trim (P0171, P0172), Misfire (P0300 to P0303), EGR (P0400) and HO2S 1 (P0131 to P0134) are set, diagnosis those DTCs first.
An intermittent malfunction may be caused by a fault in the HO2S 1 sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals |
| • | Improper mating of terminals |
| • | Broken electrical connector locks |
| • | Improperly formed or damaged terminals |
| • | Faulty terminal to wire connections |
| • | Physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Corrosion of electrical connections, splices, or terminals |
If a DTC P0133 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks, and to store the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool stores the information for later reference.
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This step determines if the fault is present.
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This step checks for an exhaust leak near the HO2S. Fresh air can enter the exhaust system through the exhaust leak and can affect HO2S 1 performance.
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||||||
Does the scan tool indicate any other DTCs besides a DTC P0133? | -- | Go to the Applicable DTC Table | ||||||||||||
3 | Visually and physically inspect for the following conditions:
Did you find a concern in any of the above areas? | -- | ||||||||||||
Check the exhaust system for an exhaust leak near the engine. Did you find an exhaust leak? | -- | |||||||||||||
5 |
Important: Before replacing the sensor, inspect the oxygen sensor for contamination. Do not replace a contaminated oxygen sensor until the cause of the contamination is found and corrected. Replace the HO2S 1. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |||||||||||
6 | Repair as necessary. Is the action complete? | -- | -- | |||||||||||
7 |
Does the scan tool display any DTCs? | -- | Go to the Applicable DTC Table | System OK |
