P0038

DTC P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
DTC P0038 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2)
DTC P0057 Oxygen Sensor Heater Control Circuit Low (Bank 2 Sensor 2)
DTC P0058 Oxygen Sensor Heater Control Circuit High (Bank 2 Sensor 2)

DESCRIPTION




The heated oxygen sensor (HO2S) is used to monitor oxygen in the exhaust gas. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal "stoichiometric" ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The ECM (Included in HV Control ECU) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric.

The HO2S generates a voltage between 0.1 and 0.9 volts in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes "Lean". The ECM interprets Lean when the HO2S voltage is below 0.45 volts. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes "Rich". The ECM interprets Rich when the HO2S voltage is above 0.45 volts.

DTC Detection Condition:

HINT:
- Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
- When any of these DTCs are set, the ECM (Included in HV Control ECU) enters fail-safe mode. The ECM turns off the Heated Oxygen (HO2) Sensor heater in fail-safe mode. Fail-safe mode continues until the engine switch is turned off.
- The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The HO2 sensor heater circuit uses a relay on the B+ side of the circuit.

HINT:
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that does not include cylinder No. 1.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Component Operating Range:

The sensing position of the Heated Oxygen (HO2) sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature, and he difference between the oxygen concentrations surrounding the inside and outside surfaces of the sensor is large, the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM (Included in HV Control ECU) supplements the heat from the exhaust with heat from a heating element inside the sensor. When the current in the sensor heater is outside the standard operating range, the ECM interprets this as a malfunction in the sensor heater and sets a DTC.

Example:
The ECM sets DTC P0038 or P0058 when the current in the HO2 sensor heater is more than 2 A.

Conversely, when the heater current is less than 0.3 A, DTC P0037 or P0057 is set.

MONITOR RESULT

Refer to Checking Monitor Status. Checking Monitor Status




The test value and test limit information are described as shown in the given table. Check the monitor result and test values after performing the monitor drive pattern.
- MID (Monitor Identification Date) is assigned to each emission-related component.
- TID (Test Identification Date) is assigned to each emission-related component.
- Scaling is used to calculate the test value indicated on generic OBD II scan tools.

Wiring Diagram:

Step 1:

Step 2-3:

Step 4:

Step 5:

INSPECTION PROCEDURE

HINT:
- If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
- Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.