Circuit Description
Oxygen sensors (O2S) are used for fuel control and post catalyst monitoring. Each O2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The O2S must reach operating temperature to provide an accurate voltage signal. A heating element in O2S 2 minimizes the time required for the sensor to reach operating temperature. The powertrain control module (PCM) supplies the O2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the O2S voltage signal. Once the O2S reaches operating temperature and Closed Loop is achieved, the O2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High O2S voltage indicates a rich exhaust stream. Low O2S voltage indicates a lean exhaust stream. This diagnostic will only run once per ignition cycle. The PCM monitors the number of rich-to-lean and lean-to-rich transitions. A transition is defined as, the O2S voltage changes from above 600 mV to below 300 mV or from below 300 mV to above 600 mV. If the PCM detects that the number of transitions were less than a specified value, DTC P1133 will set.
Conditions For Running The DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0442, P0446, P0452, P0453, P0506, P0507, P0601, P0602, P1441 are not set. |
| • | The Engine Run Time parameter is more than 200 seconds. |
| • | The ECT Sensor parameter is more than 70°C (158°F). |
| • | The Engine Speed parameter is between 1,600-2,300 RPM. |
| • | The Fuel Level Sensor parameter is more than 10 percent. |
| • | The Loop Status parameter is closed. |
| • | The TP Sensor parameter is between 10-22 percent. |
| • | The EVAP Purge Solenoid Command parameter is more than 35 percent. |
| • | The MAP Sensor parameter is more than 10 kPa. |
| • | The above conditions are met for 30 seconds. |
Conditions for Setting the DTC
The PCM detects that the O2S 1 rich-to-lean transitions is less than 2 or the lean-to-rich transitions is less than 2.
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 P1133 is most likely caused by one of the following:
| • | Fuel pressure--The system will go rich if fuel pressure is too high. The PCM can compensate for some increase, however, if pressure gets too high a DTC P0172 will be set. Refer to Fuel System Diagnosis . |
| • | Leaking injector-- A leaking or malfunctioning injector can cause the system to go rich. |
| • | Manifold absolute pressure (MAP) sensor--An output that causes the PCM to sense a higher than normal manifold pressure, or 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. |
| • | Pressure regulator--Inspect for a leaking fuel pressure regulator diaphragm by inspecting for the presence of liquid fuel in the vacuum line to the regulator. |
| • | The throttle position (TP) sensor--An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating. |
| • | O2S 1 contamination--Inspect 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, a rich exhaust indication. 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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When the system is operating correctly the O2S voltage should toggle above and below the specified values.
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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.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
|
Important: If any other DTCs are set, except HO2S DTCs, refer to other DTCs first before proceeding with this table.
Does the scan tool indicate O2 voltage varying outside the specified values? | 400-500 mV | Go to Step 3 | Go to Step 4 | |||||||
3 |
Did the DTC fail 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 | ||||||
Does the voltage measure near the specified value? | 450 mV | Go to Step 6 | Go to Step 8 | |||||||
Does the scan tool indicate O2S voltage at or near the specified value? | 0 mV | Go to Step 9 | Go to Step 7 | |||||||
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 | ||||||
10 |
Important: Determine the cause of contamination before replacing the sensor.
Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
11 | 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 | ||||||
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 | ||||||
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
