Troubleshooting

DTC P0037 OXYGEN SENSOR HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)

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.
- Bank 1 includes cylinder No. 1, but bank 2 does not. Cylinder No. 1 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.

CIRCUIT DESCRIPTION

DTC Detection Condition:

The Heated Oxygen Sensor (HO2S) 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" ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The ECM adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric.

When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust gas increases. And the HO2S informs the ECM of the LEAN condition (HO2S output is below 0.45 V).

When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio, the oxygen will be vanished from the exhaust gas. And the HO2S informs the ECM of the RICH condition (HO2S output is more than 0.45 V).

HINT: The ECM provides a pulse width modulated control circuit to adjust current through the heater. The HO2S heater circuit uses a relay on the B+ side of the circuit.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Component Operating Range:

The sensing portion of the HO2S has a zirconia element which is used to detect 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 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 current in the HO2S heater is out of the standard operating range, the ECM interprets this as a fault in the HO2S heater. The ECM illuminates MIL and sets DTC.

Normally, the HO2S heater current is 0.4 to 1.0 A.

The monitor runs if all the conditions below the met:
- Engine is started and the vehicle is driven immediately.
- Drive the vehicle over 40 km/h (64 mph) for 10 minutes.

Wiring Diagram:

Step 1 - 2:

Step 3 - 4:

Step 4 (Continued):

INSPECTION PROCEDURE

HINT: Read freeze frame data using the hand-held 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.