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Home >> Subaru >> 2010 >> Legacy Premium, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 20 (Diagnostic Trouble Code (DTC) Detecting Criteria (H4DOTC)) >> Diagnostic Trouble Code (DTC) Detecting Criteria >> DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1) >> Diagnostic Method

Diagnostic Method

WARNING: This page is about a different variant/trim than selected.

After the enable conditions have been established, calculate the front oxygen (A/F) sensor lambda value deviation cumulative value (Σ |(sglmd<n - sglmd<n-1 )|), and rear oxygen sensor output voltage deviation cumulative value (Σ |(ro2sad<n - ro2sad<n-1 )|) in every 32 x 4 times. If the front oxygen (A/F) sensor lambda value deviation cumulative value (Σ |(sglmd<n - sglmd<n-1 )|) is the predetermined value or more, calculate the judgment value.

If the duration of time while the following conditions are met is within the time indicated, judge as NG.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value
Σ |(ro2sad<n - ro2sad<n-1 )|/Σ |(sglmd<n - sglmd<n-1 )| > 9.03

Time Needed for Diagnosis:  30 - 55 seconds

Malfunction Indicator Light Illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.

Judge as OK and clear the NG if the continuous time while the following conditions are established is within the predetermined time.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value
Σ |(ro2sad<n - ro2sad<n-1 )|/Σ |(sglmd<n - sglmd<n-1 )l ≤ 9.03

Time Needed for Diagnosis:  30 - 55 seconds