P2273

DTC P2273

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 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
- Before the ECM can report DTC P2270 or P2272 failed, DTC P0036, P0037, P0038, P0056, P0057, P0058, P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, P0393, P0443, P0458, and P0459 must run and pass.
- DTCs P0461, P0462, P0463, P2066, P2067, and P2068 are not set.
- The engine is operating.
- The rear HO2S are at operating temperature for more than 10 seconds.
- The fuel injectors are enabled.
- The long term fuel control is enabled.
- The mass air flow (MAF) sensor is more than 10 g/s.
- The MAF sensor is between 6-33 g/s for more than 3 seconds during the intrusive test.
- The accumulated air flow into the engine is more than 15 grams during the fuel cut-off event.
- DTC P2271 and P2273 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
If the ECM detects that the rear HO2S voltage is more than 650 mV for more than 100 seconds, then an intrusive test is performed. The ECM will lean the fuel mixture up to -7 percent and then wait for 10 seconds at -7 percent. If the ECM detects that the HO2S voltage is still more than 650 mV, the ECM then tests the HO2S at the next decel fuel cut-off. If the ECM detects the HO2S voltage is more than 200 mV after 4 seconds in decel fuel cut-off, 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) at the beginning of the fourth ignition cycle, after 3 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 and related Freeze Frame data clears after 40 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 Connector Test Adapter Kit 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 condition, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Step 1 - Step 9:

Step 10 - Step 18:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if a condition exists.
5. This step is testing for a rear HO2S sensor circuit condition. A circuit condition sets this DTC.
8. This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.