Circuit Description
The powertrain control module (PCM) continuously monitors the oxygen sensor (O2S 1) activity for 100 seconds. During the monitor period, the PCM counts the number of times that the O2S 1 switches from rich to lean and from lean to rich, and adds the amount of time that the O2S 1 took in order to complete all of the switches. With this information, you can determine an average time for all of the switches. If the average time to switch is too slow, DTC P0133 will set.
Conditions For Running The DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set. |
| • | The fuel level is greater than 10 percent. |
| • | The engine coolant temperature (ECT) is more than 70°C (158°F). |
| • | The engine speed is between 1,600-2,450 RPM. |
| • | The engine is operating in Closed Loop. |
| • | The throttle position (TP) angle is between 9-18 percent. |
| • | The evaporative emissions (EVAP) control system is commanded open for more than 36 percent. |
| • | The purge learned memory is more than approximately 0.78. |
| • | The diagnostic completes when 30 seconds accumulated time has been spent in the above conditions. |
Conditions For Setting The DTC
| • | The average O2S 1 response times are more than 1,119 mS for rich to lean sweeps, or 760 mS for lean to rich sweeps. |
| Or |
| • | The sum of rich to lean and lean to rich is more than 1,235 mS. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
DTC P0133 or slow response is most likely caused by one of the following conditions:
| • | The fuel pressure--The system will go rich if fuel pressure is to high. The PCM can compensate for some increase, however, if the pressure becomes too high, a DTC P0172 may set. Refer to DTC P0172 . |
| • | A leaking injector--A leaking or malfunctioning injector can cause the system to go rich. |
| • | The manifold absolute pressure (MAP) sensor--An output that causes the PCM to sense a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the PCM to set a fixed value for the MAP sensor. Substitute a different MAP sensor if the rich condition is gone while the MAP sensor is disconnected. |
| • | The pressure regulator--Check for a leaking fuel pressure regulator diaphragm by checking for the presence of liquid fuel in the vacuum line to the fuel pressure regulator. |
| • | The TP sensor--An intermittent TP sensor output can cause the system to go rich due to a false indication of the engine accelerating. |
| • | O2S 1 contamination--Inspect the O2S 1 for silicone contamination from fuel or from the use of improper RTV sealant. The O2S 1 sensor may have a white powdery coating. This condition can result in a high but false voltage signal, indicating a rich exhaust condition. The PCM will then reduce the amount of fuel delivered to the engine, causing a severe surge or driveability problem. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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O2S contamination is indicated if multiple response, switching, or time ratio O2S DTCs are set.
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Even small exhaust leaks can cause slow response from the O2S.
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An O2S contaminated by silicon will have a white, powdery deposit on the portion of the O2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of an unapproved silicon RTV engine gasket material or the use of silicon-based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement O2S will also become contaminated.
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If the voltage observed in Step 9 is less than the range specified, a short between the high and low signal circuits or a short between the high signal circuit and ground is indicated. With the O2S and the PCM disconnected the resistance between the high and low signal circuits and the resistance between the high signal circuit and ground should measure infinite.
If the voltage observed in Step 8 is more than the range specified, a short between the high signal circuit and an ignition voltage source is indicated.
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If the voltage observed in Step 9 is not less than the voltage specified, a high resistance, or an open, high, or low signal circuit is indicated.
Good circuit continuity measures less than 5 ohms with the PCM and sensor disconnected. Measure between the PCM connector and the O2S connector. Ensure that the PCM terminal contact is good.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
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Important: If any other DTCs are set, except HO2S DTCs, refer to other DTCs first before proceeding with this table.
Does scan tool indicate O2S voltage varying outside the specified values? | 400-500 mV | Go to Step 3 | Go to Step 4 | |||||||
3 | Operate vehicle within Failure Records conditions. Does the scan tool indicate this DTC failed this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||||
4 | Inspect and test for the following:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 5 | ||||||
5 |
Does the voltage measure within the specified value? | 351-551 mV | Go to Step 6 | Go to Step 8 | ||||||
6 |
Does the scan tool indicate O2S voltage at or near the specified value? | 0 mV | Go to Step 9 | Go to Step 7 | ||||||
Test the low 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? | -- | Go to Step 13 | Go to Step 11 | |||||||
8 | Test the high 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? | -- | Go to Step 13 | Go to Step 11 | ||||||
9 | Test for poor connections at the O2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||
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Important: Determine the cause of contamination before replacing the sensor. Inspect and test for the following:
Replace the O2S sensor. Refer to Oxygen Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | |||||||
Test for poor 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? | -- | Go to Step 13 | Go to Step 12 | |||||||
Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | |||||||
13 |
Does the DTC run and pass? | -- | Go to Step 14 | Go to Step 2 | ||||||
14 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||
