Circuit Description
The PCM continuously monitors the Heated Oxygen Sensor (HO2S) activity for 100 seconds. During the monitoring period the PCM counts the number of times that the 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. A lean to rich transition is indicated when the HO2S voltage changes from less than 300 mV to greater 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 malfunctioning and should be replaced. If the average response time is too slow, DTC P0133 will set.
Conditions for Running the DTC
| • | No TP sensor, EVAP system, misfire, IAT sensor, MAP sensor, fuel trim, fuel injector circuit, EGR Pintle Position, ECT sensor, HO2S heater circuit sensor 1, CKP, or MAF sensor DTCs present |
| • | Engine has been running in Closed Loop fuel control for at least 60 seconds. |
| • | Engine speed is between 1000 RPM and 3000 RPM. |
| • | Engine Coolant Temperature greater than 50°C (122°F). |
| • | Mass Air Flow between 10 g/s and 30 g/s. |
Conditions for Setting the DTC
H02S 1 lean to rich average transition response time during the sample period was longer than 145 milliseconds or rich to lean average transition response time during the sample period was longer than 135 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
Check for the following conditions:
| • | Poor Connections at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the H02S 1 display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the malfunction. |
If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Fail 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
Number(s) below refer to the step number(s) 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 | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
|
Important: If any other DTCs are set (except HO2S DTCs), refer to other DTCs first before proceeding with this table.
Does scan tool indicate HO2S voltage varying outside the specified values? | 400-500 mV | |||||||||
3 | Operate vehicle within Fail 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 (PCM side) using a DMM that is connected to a good ground. Does the voltage measure near the specified value? | 5V | |||||||||
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 S ystems. 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 effected HO2S sensor. Refer to Heated Oxygen Sensor Replacement . Did you complete the repair? | -- | -- | |||||||
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. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | -- | ||||||||
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 the applicable DTC table | System OK |
