Refer to Engine Controls Schematic
Engine Data Sensors -- HO2S 1, HO2S 2
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Circuit Description
The PCM monitors the heated oxygen sensor (HO2S) activity for 100 seconds. During this test period the PCM counts the number of times that the HO2S signal voltage crosses the rich to lean and lean to rich thresholds. A lean to rich switch is determined when the HO2S voltage changes from less than 300 mV to more than 600 mV. A rich to lean switch is determined when the HO2S voltage changes from more than 600 mV to less than 300 mV. If the PCM determines that the HO2S did not switch enough times, DTC P1133 will set.
Conditions for Running the DTC
| • | No TP sensor, EVAP system, misfire, IAT sensor, MAP sensor, Fuel trim, injector circuit, EGR Pintle Position, MAF sensor, ECT sensor, CKP sensor, or H02S 1 heater circuit DTCs set. |
| • | Mass air flow is between 10 g/s and 30 g/s. |
| • | ECT is more than 50°C (122°F). |
| • | Engine run time is more than 60 seconds. |
| • | Engine speed is between 1000 RPM and 3000 RPM. |
| • | The engine is running in Closed Loop. |
Conditions for Setting the DTC
| • | The above conditions are present for a 100 second monitoring period. |
| • | The PCM monitors fewer than 40 rich to lean and 40 lean to rich switches for HO2S 1. |
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
A malfunction in the HO2S heater ignition feed or ground circuit may cause the DTC to set. Check HO2S heater circuitry for intermittent malfunctions or poor connections. If connections and wiring are OK and the DTC continues to set, replace the HO2S 1.
If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
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 scan tool indicate HO2S voltage varying outside the specified values? | 400-500 mV | |||||||||
3 | Operate the vehicle within 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? | 4.5 V | |||||||||
Measure the voltage on the HO2S low circuit, located on the PCM side, using a DMM that is connected to a good ground. Does the voltage measure near the specified value? | 5 V | |||||||||
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 poor 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. Inspect and test for the following:
Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |||||||
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? | -- | ||||||||
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Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||
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? | -- | System OK |
