Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Oxygen sensor heater control
circuit... / Circuit description
Toyota Corolla (E120): 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
The ecm uses the heated oxygen sensor information to regulate the air–fuel ratio close to a stoichiometric ratio. This maximizes the catalytic converter’s 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 air–fuel 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 duty–cycle approach to regulate the average current in the heater element. If the heater current is out of the normal range, the sensor’s output signals will be inaccurate and the ecm cannot regulate the air–fuel 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 malfunction thresholds
Component operating range
Monitor result (mode 06 data)
Refer to page 05–27 for detailed information on checking monitor status.
Wiring diagram
Refer to dtc p0130
Other materials:
Odometer and trip meter
display
■ Changing the display
Press the display change button
until the desired item is displayed.
■ Display items
Odometer
Displays the total distance the vehicle
has been driven.
Trip meter A/Trip meter B
Displays the distance the vehicle
has been driven since the meter
was last reset. Trip me ...
Cassette tape cannot be ejected
Wiring diagram
Wiring diagram
1 Check if radio auto–search functions properly
Check if the radio auto–search function properly.
Perform the auto–research of the radio and check that the
operation is normal.
Standard: malfunction disappear.
2 Press ”eject” and ...
Monitor description
While the engine is being cranked, the battery positive voltage is applied to
terminal sta of the ecm.
If the ecm detects the starter control signal (sta) while the vehicle is
driving, it will conclude that there is
a fault in the starter control circuit. The ecm will turn on the mil and a d ...