P2196

DTC P2196: Oxygen Sensor 1 (O2S1) Rich in Decel Fuel Cutoff (DFCO)





Circuit Description
The Engine Control Module (ECM) supplies a voltage of about 0.45 volts between terminals M12 and M29 (if measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts. The Oxygen Sensor 1 (O2S1) varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volts if the exhaust is lean.
In internal circuitry of the Engine control Module (ECM) can identify if the vehicle fuel system is capable of cutoff amount of the fuel supply during deceleration. When a Decel Fuel Cutoff (DFCO) mode of operation is requested during Closed Loop operation, the ECM will cutoff the fuel supply to the engine. Under these conditions the ECM should detect a lean condition. If the ECM detect a rich condition at this time, Diagnostic Trouble Code (DTC) P2196 will set. Damaged fuel pressure regulator and faulty injector will be the cause of this DTC.

Conditions for Setting the DTC
- O2S1 voltage is greater than 0.55 volts in Decel Fuel Cutoff (DFCO) mode.
- System voltage is greater than 10 volts.
- DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0337, P0351, P0352, P0401, P0402, P0404, P0405, P0406, P0441, P0443, P0488, P0502, P0506, and P0507 are not set.
- 3 second delay after in DFCO mode.

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

Conditions for Clearing the MIL/DTC
- The MIL will turn off after 4 consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for more than 10 seconds.

Diagnostic Aids
The DTC P2196 or rich exhaust is most likely caused by one of the following items:
- Leaking injector - A leaking or malfunctioning injector can cause the system to go rich causing a DTC P0132.

Steps 1-7:

Troubleshooting