P0031

DTC P0031 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
DTC P0032 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 1)
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 P0051 Oxygen Sensor Heater Control Circuit Low (Bank 2 Sensor 1)
DTC P0052 Oxygen Sensor Heater Control Circuit High (Bank 2 Sensor 1)
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

DTC Detection Condition:

The heated oxygen sensor is used to monitor oxygen concentration in the exhaust gas. For optimum catalytic converter operation, the air-fuel mixture must be maintained near the ideal stoichiometric air-fuel ratio. The heated oxygen sensor output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. The ECM adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The heated oxygen sensor generates a voltage between 0.1 and 0.9 V in response to oxygen concentration in the exhaust gas.

If the oxygen concentration in the exhaust gas increases, the air-fuel ratio is called LEAN. The heated oxygen sensor voltage drops below 0.45 V and the heated oxygen sensor informs the ECM of the LEAN condition.

If oxygen is not in the exhaust gas, the air-fuel ratio is called RICH. The heated oxygen sensor voltage increases above 0.45 V and the heated oxygen sensor informs the ECM of the RICH condition.

HINT: The ECM has a pulse width modulated control circuit to adjust current through the heater. The heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions (Part 1):

Typical Enabling Conditions (Part 2):

Typical Malfunctions Thresholds:

Component Operating Range:

The sensing portion of the heated oxygen sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust. If the zirconia element is at the proper temperature and the difference of the oxygen concentration between the inside and outside surface of the sensor is large, the zirconia element will generate voltage signals. In order to increase the oxygen concentration detecting capacity in the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor. When the current in the heated oxygen sensor heater is out of the standard operating range, the ECM interprets this as a fault in the heated oxygen sensor heater. The ECM illuminates the MIL and sets a DTC.

Normally, the heated oxygen sensor heater current is 0.4 to 1.0 A.

Example: The ECM will set a high current DTC if the current in the sensor is more than 2 A. Similarly, the ECM will set a low current DTC if the current is less than 0.3 A.

The monitor runs if the engine is started and run at idle for 9 minutes or more.

MONITOR RESULT

Refer to CHECKING MONITOR STATUS. Mode 6 Data

Wiring Diagram:

Step 1:

Step 2-3:

Step 4:

Step 5:

INSPECTION PROCEDURE

HINT:
- Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.
- Bank 1 refers to the bank that includes No. 1 cylinder.
- Bank 2 refers to the bank that does not include No. 1 cylinder.
- No. 1 cylinder is located in the front part of the engine, opposite the transmission.
- Sensor 1 refers to the sensor closest to the engine body.
- Sensor 2 refers to the sensor farthest away from the engine body.