GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptor

DTC P2297: HO2S Circuit High Voltage During Decel Fuel Cut-Off (DFCO) Sensor 2

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

HO2S Signal

P0131, P0137, P1166

P0134, P0140

P0132, P0138, P2297

P0133

Low Reference

--

P0134, P0140

--

P0133

Typical Scan Tool Data

HO2S 1 and 2

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine operating in Closed Loop

Parameter Normal Range: Fluctuates above and below 350-500 mV

HO2S 1 and 2 Signal

0 mV

400-415 mV

1000 mV

Low Reference

--

400-415 mV

1000 mV

Circuit/System Description

The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The HO2S utilizes the following circuits:

    • A signal circuit
    • A low reference circuit
    • An ignition 1 voltage circuit
    • A heater control circuit

Conditions for Running the DTC

    • DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0336, P0337, P0351, P0352, P0402, P0404, P0405, P0406, P0443, P0506, P0507, and P1404 are not set.
    • The engine airflow is greater than 13.5 g/s.
    • The startup engine coolant temperature is greater than 60°C (140°F).
    • The ignition 1 voltage is greater than 10 volts.
    • The engine has been operating for 60 seconds.
    • The engine is in Decel Fuel Cut-Off (DFCO) mode.
    • The DTCs run continuously when the above conditions are met for 3 seconds.

Conditions for Setting the DTC

The ECM detects that the HO2S voltage is greater than 550 mV during DFCO mode.

Action Taken when the DTC Sets

DTC  P2297 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC  P2297 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification

  1. With the engine running, observe the heated oxygen sensor (HO2S) 2 voltage parameter. Verify that the HO2S 2 parameter is between 350-550 mV.
  2. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector of the HO2S 2.
  2. Ignition ON, verify that the HO2S 2 parameter is between 350-500 mV.
  3. If greater than 500 mV, test the signal circuit of the HO2S 2 for a short to voltage. If the circuit/connections test normal, replace the engine control module (ECM).

    Important: The test lamp is used to load the circuit and may not illuminate.

  4. Connect a test lamp between the low reference circuit of the HO2S 2 and B+.
  5. Ignition ON, test for less than 0.1 volt between the low reference circuit of the HO2S 2 and ground.
  6. If greater than 0.1 volt, test the low reference circuit of the HO2S 2 for a short to voltage or an open/high resistance. If the circuit/connections test normal, replace the ECM.
  7. Verify that none of the following conditions exist:
  8. • Rich fuel injectors--Refer to Fuel Injector Balance Test with Special Tool .
    • Water intrusion in the HO2S harness connector
    • High fuel system pressure--Refer to Fuel System Diagnosis .
    • Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Fuel saturation of the evaporative emission (EVAP) canister
    • Exhaust leaks near the HO2S
    • Contaminated HO2S--Silicon
         ⇒If you find any of the above conditions, repair as necessary.
  9. If all circuits/connections test normal, replace the HO2S sensor 2.

Repair Instructions

    • Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
    •  Heated Oxygen Sensor 2 Replacement
    •  Control Module References for engine control module replacement, setup, and programming