P2096

One function of the heated oxygen (HO2S) bank 1 sensor 2 (threaded into the front exhaust pipe directly behind the cylinder 1, 3, 5 pre-converter) is to determine the amount of time for fuel trim biasing. Fuel trim biasing is the time the ECM holds a rich or lean command during idle or cruising conditions based on engine operating parameters intended to keep the HO2S bank 1 sensor 2 voltage at a constant 600 mV. As the HO2S bank 1 sensor 1 becomes active, the ECM will go into closed loop fuel control. At this time, the ECM will toggle between a rich and lean command (called perturbation) used to improve catalytic converter efficiency. Under normal steady cruise conditions, the HO2S bank 1 sensor 2 should fluctuate slightly between 500 mV and 800 mV. If the ECM is commanding lean, the HO2S bank 1 sensor 2 voltage should remain steady for a certain length of time as the catalytic converter is storing oxygen. Eventually, the amount of oxygen the converter can store is overcome by the lean condition and the HO2S bank 1 sensor 2 value will eventually drop. This process works exactly opposite for the rich fuel command when the converter is releasing oxygen. Using this process, the ECM can control the voltage level out of the HO2S bank 1 sensor 2. The fuel trim bias time is designed to be centered around zero seconds. A positive time indicates the ECM is holding a rich command for longer than calibrated. A negative time indicates the ECM is holding a lean command for longer than calibrated. The ECM will continuously run a check to make sure the fuel trim bias time is within limits. DTC P2096 will set if fuel trim bias time is too far in the negative range indicating the ECM has exceeded its lean limit threshold. This indicates the HO2S bank 1 sensor 1 signal voltage has shifted down.

DTC PARAMETERS
DTC P2096 will set if the ECM needs to hold the lean command for longer than 1.05 seconds in order to achieve a 600 mV HO2S bank 1 sensor 2 target voltage when:
^ Condition exists for longer than 200 seconds
^ Bank 1 loop status is closed
^ HO2S bank 1 sensor 2 loop status is closed
^ EVAP leak diagnostics are not running
^ No bank 1 catalyst efficiency, CAM, ECT, EVAP purge solenoid, fuel trim, HO2S heater, MAF or misfire DTCs have been set

DTC P2096 diagnostic runs continuously once the above conditions have been met.

P2096 is a type B DTC.

DIAGNOSTIC AIDS

IMPORTANT: If an HO2S bank 1 sensor 1 circuit or slow response DTC or an HO2S bank 1 sensor 2 circuit or slow response DTC is set, diagnose that DTC first.

Make sure no exhaust leaks exist between the bank 1 engine head and 18 inches after the HO2S bank 1 sensor 2.

Start engine and allow ECT to reach at least 80°C (176°F). Using Scan tool, monitor HO2S BANK 1 SENSOR 2. Make sure reading is not consistently below 400 mV or consistently above 900 mV. If reading is consistently lower than 400 mV, refer to DTC P0137 flowchart. If reading is consistently above 900 mV, refer to DTC P0138. Reading should be within the 500 mV to 800 mV range. If reading is OK, the most probable cause for DTC P2096 is a weak, aging or contaminated HO2S bank 1 sensor 1. P0137 P0138

Check for obvious contamination (oil, fuel or engine coolant) by removing sensor. Source and fix the cause of the contamination if contaminated. Replace the HO2S bank 1 sensor 1.