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:
Inspection procedure
Hand–held tester:
1 Perform active test by hand–held tester(operation of circuit
opening relay)
Connect the hand–held tester to the dlc3.
turn the ignition switch on and push the hand–held tester main
switch on.
select the item ”diagnosis / enhanced obd ii / active ...
Manual shifting test
1. Perform manual shifting test
Hint:
by this test, it can be determined whether the trouble is within
the electrical circuit or is a mechanical problem in the transaxle.
Disconnect the transmission wire connector.
inspect the manual driving operation.
Check that the shift and g ...
USB Port/AUX Port
Connect an iPod, USB memory device or portable audio player to the USB/AUX
port as indicated below. Select “iPod”, “USB” or “AUX” on the audio source selection
screen and the device can be operated via multimedia system.
Connecting using the USB/AUX port
■ iPod
Open the cove ...