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:
Do-it-yourself service precautions
If you perform maintenance by yourself, be sure to follow the correct procedure
as given in these sections.
CAUTION
The engine compartment contains many mechanisms and fluids that may move suddenly,
become hot, or become electrically energized. To avoid death or serious injury,
observe t ...
Wheels
If a wheel is bent, cracked or
heavily corroded, it should
be replaced. Otherwise, the
tire may separate from the
wheel or cause a loss of
handling control.
Wheel selection
When replacing wheels, care
should be taken to ensure that
they are equivalent to those
removed in load capacity, diameter,
rim ...
Unlocking and locking the doors from the outside
◆ Smart key system (if equipped)
Carry the electronic key to enable this function.
1 Grip the driver’s door handle to unlock the door. Grip the passenger’s door
handle to unlock all the doors.* Make sure to touch the sensor on the back of the
handle.
The doors cannot be unlocked for ...