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:
Problem symptoms table
Hint:
use the table below to help determine the cause of the problem. The numbers
indicate the priority of the
likely cause of the problem. Check each part in order. If necessary, replace
these parts.
1. Headlamp and tail lamp
2. Front fog lamp system
3. Turn signal and hazard warni ...
Light control switch circuit
Wiring diagram
Inspection procedure
1 Check headlamp dimmer switch assy (light control switch)
2 Check wire harness (tvip ecu light control switch)
Disconnect the tvip ecu and light control switch connectors.
check the continuity between the terminals of the tvip
e ...
Circuit description
The ecm compares the two waveforms of the heated oxygen sensors located
before and after the catalyst
to determine whether or not the catalyst performance has deteriorated.
Air–fuel ratio feedback compensation keeps the waveform of the heated oxygen
sensor in front of the catalyst
alterna ...