[amidgeha]

O2 Sensor Delayed Response - Rich to Lean

During a Deceleration Fuel Shut-Off (DFSO) event, the Powertrain Control Module (PCM) monitors the rear heated oxygen sensor (HO2S) signal to determine if the signal is stuck in range. The PCM expects the signal to exceed a calibrated rich or lean value within a calibrated amount of time. If the signal voltage remains less than the rich value after a number of occurrences, the PCM intrusively controls the fuel system rich over increasing time periods in an attempt to force the signal to greater than the calibrated rich value. The test fails when, after three consecutive intrusive attempts, the signal cannot be forced greater than the calibrated rich value. Also, if the signal voltage remains greater than the lean value after a calibrated amount of time with the fuel injectors off, a counter is incremented. The test fails when after three consecutive occurrences the signal is not less than the calibrated lean value.

Cause:
Faulty Heated Oxygen Bank 2 Sensor 2
Heated Oxygen Bank 2 Sensor 2 harness is open or shorted
Heated Oxygen Bank 2 Sensor 2 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Exhaust leaks before or near the Heated Oxygen Bank 2 Sensor 2

Symptoms:
Check engine light
High Fuel Consumption
Excessive Smoke from Exhaust