P2271, P2273 O2 Sensor Signal Stuck Rich

P2271, P2273 code - The Powertrain Control Module (PCM) detects the Downstream O2 sensor does not transition from a rich to lean condition within a specific time during a DFSO event. Default action this DTC the MIL light illuminate.

P2271, P2273 code

DTC Description:
- P2271 O2 Sensor 1/2 signal stuck rich
- P2273 O2 Sensor 2/2 signal stuck rich

When monitored and set conditions P2271, P2273 code

- Ambient temperature above -7°C (19.4°F).
- Battery voltage above 11.0 volts.
- Fuel level above 12%.
- With the engine running for more than 90.0 seconds.
- ECT temperature above 70°C (158°F).
- Catalytic converter temperature between 500°C (932°F) and 850°C (1562°F).
- Upstream closed loop fuel control active.
- Once the enable conditions are met the vehicle must be driven under the following condition:

  • Engine speed above 1152 rpm.
  • Vehicle speed above 64.4 km/h (60 mph)
  • Throttle open for a minimum of 120 seconds.
  • Immediately after a closed throttle decel fuel shutoff (DFSO) event.

Possible causes P2271, P2273 code

- Exhaust system leak
- O2 sensor signal circuit
- O2 sensor return circuit
- O2 sensor

Diagnostic test P2271, P2273 code

Step 1. Check for an active DTC
Check for contaminants that may have damaged the O2 sensor: contaminated fuel, unapproved silicone, oil and coolant. After the repairs have been made, verify proper O2 sensor operation. If all the O2 sensor voltage readings have not returned normal, follow the diagnostic procedure for the remaining O2 sensors.

Start the engine, test drive or operate the vehicle in accordance with the when monitored and set conditions. With the scan tool read DTCs.

Is the DTC active or pending?

Yes, go to step 2.
No, perform the PCM intermittent condition.

Step 2. Checking the exhaust system for leaks
Perform the CHECKING THE EXHAUST SYSTEM FOR LEAKS test procedure.

Were any exhaust leaks found?

Yes, perform the appropriate repairs.
No, go to step 3.

Step 3. Check the O2 sensor signal circuit
Turn the ignition off, disconnect the O2 sensor harness connector. Turn the ignition on, measure the voltage between ground and the O2 sensor signal circuit in the O2 sensor harness connector.

Is the voltage between 4.1 and 5.0 volts?

Yes, go to step 4.
No, check the O2 sensor signal circuit for a short to ground, open or short to voltage. If OK, replace and program the Powertrain Control Module (PCM)

Step 4. Check the O2 sensor return circuit
Measure the voltage between ground and the O2 sensor return circuit in the O2 sensor harness connector.

Is the voltage at 2.5 volts?

Yes, go to step 5.
No, check the O2 sensor return circuit for a short to ground, open or short to voltage. If OK, replace and program the PCM.

Step 5. O2 sensor
Check for signs of contaminants that may have damaged the O2 sensor, such as contaminated fuel, unapproved silicone, oil and coolant. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the O2 sensor and the Powertrain Control Module (PCM).
- Look for any chafed, pierced, pinched or partially broken wires.
- Look for broken, bent, pushed out or corroded terminals.
- Verify that there is good pin to terminal contact in the O2 sensor and Powertrain Control Module connectors.
- Perform any service bulletins that may apply.

Were any problems found?

Yes, repair as necessary.
No, replace the oxygen sensor.

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