Circuit Description
The secondary heated oxygen sensor (HO2S) measures the oxygen content of the exhaust downstream of the three-way catalyst (TWC), so that the TWC efficiency is optimized. The powertrain control module (PCM) supplies a voltage near 450 mV between the HO2S signal circuit and the low reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.
The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage for being fixed below a predetermined voltage. If the PCM detects the voltage is too low, this DTC sets.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC P2271 HO2S Signal Stuck Rich Bank 1 Sensor 2 |
| • | DTC P2273 HO2S Signal Stuck Rich Bank 2 Sensor 2 |
Conditions for Running the DTC
| • | DTCs P0030, P0050, P0107, P0108, P0112, P0113, P0117, P0118, P0133, P0135, P0137, P0138, P0141, P0153, P0155, P0157, P0158, P0161, P0171, P0172, P0174, P0175, P0300, P0301-P0306, P0335, P0401, P0404, P0442, P0443, P0496, P1128, P1129, P2413, P2414, P2415 are not set. |
| • | The engine is operating for more than 2 minutes. |
| • | The engine speed is between 1,100-2,400 RPM. |
| • | The engine coolant temperature (ECT) is more than 69°C (156°F). |
| • | The intake air temperature (IAT) is more than -7°C (+19°F). |
| • | The fuel system is in closed loop. |
| • | DTCs P2271 and P2273 run once per drive cycle when the above conditions are met. |
Conditions for Setting the DTC
| • | The PCM detects that the affected HO2S 2 signal voltage is always more than 293 mV. |
| • | The condition exists for more than 7 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if an active malfunction exists.
-
This step is testing for a rich fueling condition or the cause of a higher than normal sensor voltage.
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 - Vehicle? | -- | Go to Step 2 | |||||||||||||||||||
|
Important:
Did the voltage drop to less than the specified value at least once? | 293 mV | Go to Step 3 | Go to Step 4 | |||||||||||||||||||
3 |
Did DTC P2271 or DTC P2273 fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||||||||||||||
4 |
Is the voltage more than the specified value? | 1,050 mV | Go to Step 5 | Go to Step 6 | ||||||||||||||||||
5 | Test the appropriate HO2S 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||||||||||||||
Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 | |||||||||||||||||||
7 |
Important: When you have completed the fuel system diagnosis, return to this diagnostic. Test the fuel system for operating rich. Refer to Fuel System Diagnosis . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | ||||||||||||||||||
8 | Test shorted terminals and for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||||||||||||||||
9 | Test shorted terminals and for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||||||||||||||||
10 | Replace the appropriate HO2S. Refer to the appropriate procedure: Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||||||||||||
11 |
Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||||||||||||
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 | ||||||||||||||||||
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||||||
