Advanced Diagnostics

Advanced Diagnostics - DTC P2270: Rear Secondary Heated Oxygen Sensor (Secondary HO2S (Bank 1, Sensor 2)) Circuit Signal Stuck Lean










General Description
The rear secondary heated oxygen sensor (secondary HO2S (bank 1, sensor 2)) detects the oxygen content in the exhaust gas downstream of the warm up three way catalytic converter (WU-TWC) (bank 1) during stoichiometric air/fuel ratio feedback control. The powertrain control module (PCM) controls the air/fuel ratio from the rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) output voltage so that the WU-TWC efficiency is optimized. After current is applied to the rear secondary HO2S heater, if the rear secondary HO2S output continues to be low (lean) during feedback control, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
The rear secondary HO2S output voltage is 0.05 V or less for at least 35 seconds.

Driving Pattern
1. Start the engine, and let it idle until the radiator fan comes on.
2. Drive immediately at a steady engine speed between 1,500 - 3,000 rpm for at least 35 seconds.

- When freeze data is stored, drive the vehicle under those conditions instead of Driving Pattern step 2.
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.