Failing to investigate the cause of the following warnings may lead to the system operating abnormally and possibly cause an accident.
Have the vehicle inspected by your Toyota dealer immediately.


Stop the vehicle immediately.
Follow the correction procedures.Removal
REMOVAL
CAUTION / NOTICE / HINT
NOTICE:
If automatic transaxle assembly parts are replaced, refer to Parts Replacement
Compensation Table to determine if any additional operations are necessary (See
page ).
PROCEDURE
1. REMOVE ENGINE ASSEMBLY WITH TR ...
Catalyst System Efficiency Below Threshold (Bank 1) (P0420)
MONITOR DESCRIPTION
The ECM uses sensors mounted in front of and behind the Three-Way Catalytic Converter
(TWC) to monitor its efficiency.
The first sensor, the air fuel ratio sensor, sends pre-catalyst information to
the ECM. The second sensor, the heat ...
System Diagram
SYSTEM DIAGRAM
Communication Table
Transmitting ECU
(Transmitter)
Receiving ECU
(Receiver)
Signal
Communication Method
Combination meter
Power management control ECU
...