P2096

DTC P2096: Post Catalyst Fuel Trim System Low Limit

Circuit Description
The engine control module (ECM) supplies a voltage of about 0.45 V to the heated oxygen sensor. The heated oxygen sensor (HO2S) varies the voltage within a range of about 1 V if the exhaust is rich, down to about 0.1 V if the exhaust is lean.

This diagnosis can detect the sluggish behavior of the lean shift of HO2S1 and detect the abnormality of HO2S2 (below 0.65 V). A malfunction is registered if the fuel trim control values exceed the maximum threshold value for the diagnosis time during fuel trim control activation phase. If catalysts are deteriorated, HO2S2 signal oscillates according to the actual lambda signal. So, the diagnosis must be considered with catalyst deterioration factor.

Conditions for Setting the DTC
- Barometric pressure is greater than 72 kPa.
- Intake air temperature (IAT) is greater than -40 °C
- Ignition voltage is greater than 10 V.
- Long term fuel trim adjustment has reached its limit while the sensor voltage is still trying to move the adjustment further in the same direction.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after four consecutive driving cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- The DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
An intermittent malfunction may be caused by a problem in the HO2S electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to [Intermittents]. Intermittents

Troubleshooting

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