Circuit Description
The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) high 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 ECM monitors and stores the HO2S voltage information. The ECM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The ECM 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 ECM test for the following conditions:
| • | The ECM monitors the HO2S voltage to determine if the signal voltage goes below a predetermined threshold within a certain amount of time. If the ECM determines that the signal voltage remains above a threshold, the ECM commands a lean condition. If the signal voltage does not go below the threshold within a certain amount of time after commanding the system lean, this DTC sets. |
| • | The ECM monitors the HO2S voltage during fuel cut-off. If the ECM determines that the signal voltage is more than a predetermined voltage during fuel cut-off, this DTC sets. |
DTC Descriptor
This diagnostic procedure supports the following DTC:
| • | 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
| • | Before the ECM can report DTC P2270 or P2272 failed, DTC P0036, P0037, P0038, P0056, P0057, P0058, P137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0342, P0343, P0367, P0368, P0366, P0443, P0451, P0452, P0453, P0458, and P0459 must run and pass. |
| • | DTC P0461, P0462, P0463, P2066, P2067, and P2068 are not set. |
Conditions 1
| • | The engine is running. |
| • | The rear HO2S are at operating temperature for more than 10 seconds. |
| • | The mass air flow (MAF) sensor flow is more than 9.72 g/s. |
| • | The MAF sensor flow is 5.6-33 g/s for more than 3 seconds during the intrusive test. |
| • | The ignition 1 voltage is more than 10.5 volts. |
| • | The rear HO2S closed loop control is enabled. |
| • | The engine decel fuel cut-off state is not detected. |
| • | The post oxygen sensors adjust--express diluted correction. |
| • | The post oxygen sensors adjust--express rich correction. |
| • | The post oxygen sensors adjust--hesitation correction. |
| • | After decel fuel cut-off is invalid, a malfunction exists in the post oxygen sensors deterioration diagnosis. |
Conditions 2
| • | The engine is running. |
| • | The ignition 1 voltage is more than 10.5 volts. |
| • | The rear HO2S heater is at operating temperature. |
| • | The rear HO2S detects dewing for 30 seconds. |
| • | The accumulated air flow into the engine is more than 15 grams during the fuel cut-off state. |
| • | The calculated rear HO2S temperature is more than 350°C (662°F) |
| • | The ECM does not receive the signal of a fuel leak detection. |
| • | DTC P2271 and P2273 runs continuously once one of the above conditions are met |
Conditions for Setting the DTC
If the ECM detects that the rear HO2S voltage is less than 0.582-0.661 volts for more than 100 seconds, then an intrusive test is performed. The ECM enriches the fuel mixture up to predetermined value with the change rate of 0.017 per second and then wait for 10 seconds at the value. If the ECM detects that the HO2S voltage is still more than 650 mV, the ECM then test the HO2S at the next decel fuel cut-off.
If the ECM detects the HO2S voltage is more than 140 mV after 4 seconds in decel fuel cutoff, this DTC sets.
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 4 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
| • | Use the J 35616 for any test that requires probing the ECM harness connector or a component harness connector. |
| • | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views . |
| • | A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a rich condition. |
| • | For an intermittent, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if a condition exists.
-
This step is testing for a rear HO2S sensor circuit condition. A circuit condition sets this DTC.
-
This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.
DTC P2271 or P2273
Step | Action | Values | Yes | No | ||||||||||||||
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views . | ||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||||||
Did DTC P2271 or DTC P2273 fail this ignition? | -- | Go to Step 4 | Go to Step 3 | |||||||||||||||
3 |
| -- | Go to Step 4 | Go to Diagnostic Aids | ||||||||||||||
4 | Is DTC P0137, P0138, P0140, P0157, P0158, or P0160 also set? | -- | Go to Step 5 | |||||||||||||||
Is the voltage less than the specified value? | 1050 mV | Go to Step 8 | Go to Step 6 | |||||||||||||||
6 |
Is the voltage within the specified range? | 350-550 mV | Go to Step 12 | Go to Step 7 | ||||||||||||||
7 | Test the appropriate HO2S signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 13 | ||||||||||||||
Move the related HO2S harnesses for the rear sensor between the HO2S harness connector and the engine control module (ECM) while monitoring the appropriate HO2S voltage parameter. Does the HO2S parameter change abruptly while moving the related harnesses? | -- | Go to Step 14 | Go to Step 9 | |||||||||||||||
9 |
Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 10 | ||||||||||||||
10 | Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 11 | ||||||||||||||
11 |
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 17 | Go to Step 12 | ||||||||||||||
12 | Test for shorted terminals and for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 | ||||||||||||||
13 | Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||||||||||
14 | Repair the circuit if necessary. Refer to Wiring Repairs . Did you complete the repairs? | -- | Go to Step 17 | -- | ||||||||||||||
15 | Replace the HO2S. Refer to the appropriate procedure: | -- | Go to Step 17 | -- | ||||||||||||||
16 | Replace the ECM. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||||||||
17 |
Does the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 18 | ||||||||||||||
18 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||
