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Home >> Subaru >> 2008 >> Forester X, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Diagnostic Trouble Code (DTC) Detecting Criteria (H4SO) >> Diagnostic Trouble Code (DTC) Detecting Criteria >> DTC P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1) >> Diagnostic Method

Diagnostic Method

Calculate faf difference every 128 milliseconds, and the λ value difference. Calculate the diagnostic value after calculating for 210 seconds.

Judge as NG when the malfunction criteria below are met. Judge as OK and clear the NG when the malfunction criteria below are not met.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value
parafca = td2faf/td2lmd
where,
td2faf (N) = td2faf (n-1) + |d2faf (n)|
td2lmd (N) = td2lmd (n-1) + |d2lmd (n)|
add up to a total of 210 seconds
d2faf (n) = (faf (n) - faf (n-1)) - (faf (n-1) - faf (n-2))
d2lmd (n) = (lmd (n) - lmd (n-1)) - (lmd (n-1) - lmd (n-2))
faf = main feedback compensation coefficient every 128 milliseconds
lmd = output lambda every 128 milliseconds
≥ 0.44

Time Needed for Diagnosis:  210 seconds

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