Toyota Tacoma manuals

Toyota Corolla Repair Manual: Circuit description

Refer to dtc p0130

Hint

: the ecm provides 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 description

The ecm uses the heated oxygen sensor information to regulate the airfuel ratio close to a stoichiometric ratio. This maximizes the catalytic converters ability to purify the exhaust gas. The sensor detects oxygen levels in the exhaust gas and sends this signal to the ecm.

The inner surface of the sensor element is exposed to the outside air. The outer surface of the sensor element is exposed to the exhaust gas. The sensor element is made of the platinum coated zirconia and includes an integrated heating element. The heated oxygen sensor has the characteristic whereby its output voltage change suddenly in the vicinity of the stoichiometric airfuel ratio. When heated, the sensor becomes very efficient. If the temperature of the exhaust is low, the sensor will not generate useful voltage signals without supplemental heating. The ecm regulates the supplemental heating using a dutycycle approach to regulate the average current in the heater element. If the heater current is out of the normal range, the sensors output signals will be inaccurate and the ecm cannot regulate the airfuel ratio properly. When the heater current is out of the normal operating range, the ecm interprets this as a malfunction and sets a dtc.

Example: the ecm will set a high current dtc if the current in the sensor is more than 2 a when the heater is off.

Similarly, the ecm will set a low current dtc if the current is less than 0.25 A when the heater is on.

Monitor strategy

Typical enabling conditions

Typical enabling conditions

Typical malfunction thresholds

Typical malfunction thresholds

Component operating range

Component operating range

Monitor result (mode 06 data)

Monitor result (mode 06 data)

Refer to page 0527 for detailed information on checking monitor status.

Refer to page 0527 for detailed information on checking monitor status.

Wiring diagram

Refer to dtc p0130

Oxygen sensor heater control circuit...
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 ...

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