Circuit Description
The Powertrain Control Module (PCM) continuously monitors the oxygen sensor 1 (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, then adds the amount of time that the O2S 1 took to complete all the switches. With this information, an average time for all switches can be determined. Whenever the average time to switch is too slow, a DTC P0133 will set.
Conditions For Running The DTC
| • | No actice MAP DTC's |
| • | No active IAT DTC's |
| • | No active ECT DTC's |
| • | No active TP DTC's |
| • | No active Fuel Trim DTC's |
| • | No active Injector Control DTC's |
| • | No active Misfire DTC's |
| • | No active CKP DTC's |
| • | No active Evap DTC's |
| • | No active IAC DTC's |
| • | No active PCM Memory DTC's |
| • | The engine has been running more than 10 seconds. |
| • | ECT is more than 75°C (167°F). |
| • | Engine speed is between 1600 RPM and 2600 RPM. |
| • | Engine is operating in closed loop. |
| • | Throttle Position (TP) angle is between 14 percent and 26 percent. |
| • | Evaporative emissions control system is commanded open for more than 40 percent. |
| • | Purge learned memory is more than approximately 0.86. |
| • | 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 249 mS for rich to lean sweeps or 249 mS for lean to rich sweeps.
Or
Ratio of response times is more than 4.25 or less than 0.44.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
DTC P0133 or slow response is most likely caused by one of the following:
| • | The fuel pressure - The system will go rich if the fuel pressure is to high. The PCM can compensate for some increase, if the fuel pressure gets too high, a DTC P0172 may set. Refer to Fuel System Diagnosis . |
| • | A leaking fuel injector - A leaking or faulty fuel injector can cause the system to go rich. |
| • | The 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 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 regulator. |
| • | The TP sensor - An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating. |
| • | The O2S 1 contamination - Inspect the O2S 1 for silicone contamination from fuel or use of improper RTV sealant. The sensor may have a white powdery coating and result in a high but false voltage signal (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem. |
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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HO2S contamination is indicated if multiple Response, Switching or Time Ratio HO2S DTCs are set.
-
The use of leaded fuel may be indicated by the removal or tampering of the fuel filler restrictor.
An HO2S contaminated by silicon will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of un-approved 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 HO2S will also get contaminated.
-
Even small exhaust leaks can cause slow response from the HO2S.
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An HO2S contaminated by silicon will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of un-approved silicon RTV engine gasket material or the use of the use of silicon based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also get contaminated.
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If the voltage observed in step 8 is less than the range specified a short between the HIGH and LOW circuits or a short between the HIGH circuit and ground is indicated. With the HO2S and the VCM disconnected the resistance between the HIGH and LOW circuits and the resistance between the HIGH circuit and ground should measure infinite.
If the voltage observed in step 8 is more than the range specified a short between the HIGH circuit and an ignition voltage source is indicated.
-
If the voltage observed in step 9 is not below the voltage specified a high resistance (open) HIGH or LOW circuit is indicated.
Good circuit continuity measures less than 5 ohms with the VCM and sensor disconnected. Measure between the VCM connector and the HO2S connector. Ensure VCM terminal contact is good.
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||
Do the parameters show averages more than the specified value? | 249 ms | |||||||||||||
3 | Are any powertrain component DTC's set? | -- | Go to the applicable DTC table | |||||||||||
Has the contamination source been removed and the affected sensor replaced? | -- | -- | ||||||||||||
5 |
| -- | ||||||||||||
6 | This DTC is intermittent. Are any additional DTCs stored? | -- | Go to the applicable DTC table | Go to Diagnostic Aids | ||||||||||
Repair exhaust as necessary. Refer to Exhaust System Inspection in Engine Exhaust. Repair as necessary. Refer to Connector Repairs in Wiring Systems. Did you find a problem? | -- | |||||||||||||
8 |
Is the O2S voltage within the value specified? | 351-551mv | ||||||||||||
9 |
Is the O2S voltage less than the value specified? | 20mv | ||||||||||||
10 |
O2S contamination sources include the following:
Is the action complete? | -- | -- | |||||||||||
11 | Repair the short between the O2S HIGH and LOW circuits or between the O2S HIGH signal circuit and a voltage source. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||
Is the action complete? | -- | -- | ||||||||||||
Replace the O2S. Refer to Oxygen Sensor Replacement . Is the action complete? | -- | -- | ||||||||||||
Does the scan tool indicate the diagnostic Passed? | -- | |||||||||||||
15 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable table | System OK |
