Circuit Description
The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity for 100 seconds. During the monitoring period the PCM counts the number of times that a rich to lean and lean to rich response is indicated and adds the amount of time it took to complete all transitions. With this information, an average time for each transition can be determined. If the average response time is too slow, DTC P0133 will be set.
A lean to rich transition is indicated when the HO2S voltage changes from less than 300 mV to more 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
| • | No active TP, MAP, MAF, IAT, ECT, AIR, CKP Sensor, Misfire, Fuel Injector Circuit, EVAP, or HO2S DTCs are present. |
| • | The engine has been running in Closed Loop for at least 1 minute. |
| • | The engine speed is between 1000-3000 RPM. |
| • | The engine coolant temperature is more than 50°C (122°F). |
| • | The vehicle is not in Park or Neutral. |
| • | The TP is more than 2 percent. |
| • | The AIR pump is commanded OFF. |
| • | The MAF is between 10-30 gm/s. |
| • | The ignition voltage is between 9-18 volts. |
Conditions for Setting the DTC
| • | The H02S 1 lean to rich average transition response time was more than 87 milliseconds. |
| • | The H02S 1 rich to lean average transition response time was more than 110 milliseconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
Inspect for the following conditions:
HO2S contamination -- Refer to
Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.
in Cautions and Notices.Important : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Faulty terminal connections--Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal-to-wire connections. Use a corresponding mating terminal in order to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. |
| • | A damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving the connectors and the wiring harnesses that are related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. |
| • | Inspect the PCM and the engine grounds for clean and secure connections. |
If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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When the system is operating correctly the HO2S voltage should toggle above and below the specified values.
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If the low circuit is shorted to ground the HO2S voltage will be less than 400 mV when the signal circuit is jumped to ground.
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The specified value is what is measured on a correctly operating system.
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The specified value is what is measured on a correctly operating system.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||||||||
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Important: If any other DTCs are set except HO2S DTCs, refer to the other DTCs first before proceeding.
Does the scan tool indicate HO2S voltage varying outside the specified values? | 400-500 mV | |||||||||
3 | Operate the vehicle within the Failure Records conditions. Does the scan tool indicate this DTC failed this ignition? | -- | Go to Diagnostic Aids | |||||||
4 | Inspect and test for the following:
Did you find and correct the condition? | -- | ||||||||
Does the scan tool indicate HO2S voltage more than the specified value? | 400 mV | |||||||||
Does the voltage measure near the specified value? | 4.5V | |||||||||
Measure the voltage on the HO2S low circuit on the PCM side, using a DMM that is connected to a good ground. Does the voltage measure near the specified value? | 5.0V | |||||||||
8 | Test the low circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
9 | Test the signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
10 | Test the low circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
11 | Test for faulty connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
12 |
Important: Determine the cause of contamination before replacing the sensor.
Did you complete the replacement? | -- | -- | |||||||
13 | Test for faulty connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
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Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||||||||
15 |
Does the DTC reset? | -- | ||||||||
16 | Use the scan tool in order to check for DTCs. Does the scan tool indicate any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
