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:
If your vehicle overheats
The following may indicate
that your vehicle is overheating.
The engine coolant temperature
gauge is in the red zone or a loss
of engine power is experienced.
(For example, the
vehicle speed does not
increase.)
"Engine Coolant Temp High
Stop in a Safe Place See
Owner's Manual" is shown
on ...
Overhaul
1. Remove w/head taper screw plug no.2
Using a socket hexagon wench 10, remove the taper
screw plug and gasket.
2. Remove valve lifter
Remove the valve lifters from the cylinder head.
3. Remove valve
Place the cylinder head on wooden blocks.
using sst, compres ...
Temporarily engaged gear steps selection mode in the D position
To drive in temporary gear steps selection mode, operate the “-” and “+” paddle
shift switches. The gear steps can then be selected by operating the “-” and “+”
paddle shift switches. By selecting gear step using paddle shift switches, you can
control engine braking forces.
1 ...