Subaru IMPREZA GD 2007 Series Manual page 1919

asieps_tobira_IM_US.book 128 ページ ２０１２年１月１７日 火曜日 午後３時４８分
Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
BJ:DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)
1. OUTLINE OF DIAGNOSIS
Detect the deterioration of the catalyst function.
Though the rear oxygen sensor output would change slowly with a new catalyst, the sensor output with a de-
teriorated catalyst becomes high and the inversion time is shortened.
For this reason, the catalyst diagnosis is carried out by monitoring the rear oxygen sensor output and com-
paring it with the front oxygen (A/F) sensor output.
2. COMPONENT DESCRIPTION
(A)
(B)
(1) Front oxygen (A/F) sensor
(2) Rear oxygen sensor
(3) Catalytic converter
(1)
(3)
(3)
(C)
(A) Normal
(B) Deterioration
(C) Output waveform from the front
oxygen (A/F) sensor
GD(H4DOTC)-128
(2)
(D)
(D) Output waveform from the rear
oxygen sensor
EN-01713