Hi,
for LH3.2 control unit the 5-1-2 is set when fuel trim remains low for 166sec.
fuel trim is a measure for optimum air/fuel mix i.e. lambda=1.
possible sources: HO2S faulty, signal wire short-circuited or MAF faulty, contact resistance high.
I have twice succesfully cleaned slow operating front HO2S (200kkm/10y) sensors by first putting the sensor into carbon cleaning liquid for some time and then burning it clean with garden grill flame - do not rub the sensor. New sensor is allways new but right one.
small vacum leaks make the engine to idle uneven faster than 166 sec periods.
br Tapsa
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