Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Catalyst system efficiency below
threshold
Toyota Corolla (E120): Catalyst system efficiency below threshold
Dtc p0420 catalyst system efficiency below threshold (bank 1)
Other materials:
Circuit description
A thermistor is built in the engine coolant temperature sensor and changes
the resistance value according
to the engine coolant temperature.
The structure of the sensor and connection to the ecm is the same as those of
the intake air temperature
sensor.
Hint:
if the ecm detects the dtc ...
Air conditioning filter
The air conditioning filter must be changed regularly to maintain air conditioning
efficiency.
Removal method
1Turn the engine switch off.
2 Open the glove box. Slide off the damper.
3 Push in the glove box on the vehicle’s outer side to disconnect the claws.
Then pull out the glove box ...
Inspection procedure
1 Check hazard warning signal switch assy
Check the hazard warning switch continuity, as shown in
the illustration and table.
Standard:
2 Check turn signal flasher assy
3 Check wire harness (tvip ecu turn signal flasher)
Disconnect the tvip ecu and turn signal flashe ...