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:
Ecm/pcm processor
Dtc p0606 ecm/pcm processor
Monitor description
The ecm continuously monitors its internal circuits. This self–check insures
that the ecm is functioning properly.
If a malfunction is detected, the ecm will set the appropriate dtc and
illuminate the mil.
The two cpus, main and sub cpu i ...
Inspection
1. Spark plug
Notice:
never use a wire brush for cleaning.
Never attempt to adjust the electrode gap on used
spark plug.
Spark plug should be replaced every 192,000 km
(120,000 miles).
Clean the spark plugs.
Air pressure: below 588 kpa (6.0 Kg/cm2, 85 psi)
duration: 20 sec ...
Fuel information
You must only use unleaded
gasoline.
Select octane rating of 87
(Research Octane Number
91) or higher. Use of
unleaded gasoline with an
octane rating lower than 87
may result in engine knocking.
Persistent knocking
can lead to engine damage.
At minimum, the gasoline you
use should meet the specifi ...