8-VALVE 1.4
ENGINE
FIAT PUNTO TRAINING OUTLINE
Fiat Auto S.p.A.
After Sales Training
4.5.3 Cylinder position recognition
The engine phase signal, together with the top dead centre (T.D.C.) and engine revs signal,
allows the engine control unit to recognize the cylinder sequence to implement the timed
injection.
This signal is generated by a Hall-effect sensor positioned on the tappet cover just next to the
phonic wheel obtained on the distributing shaft pulley.
4.5.4 Oxygen sensor – combustion check
In EOBD systems, two oxygen sensors (which are of the same type but cannot be exchanged
with one another) are available: one before the catalyst system (pre-catalyst) and one after the
same (post-catalyst). The pre-catalyst sensor determines the loop 1 mixture ratio control (pre-
catalyst sensor closed loop).
The post-catalyst sensor is used to diagnose the catalyst and finely modulate the loop 1
control parameters.
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To this regard, the purpose of loop 2 adaptivity is to recover both the production dispersions
and the slow drift that the pre-catalyst sensor response may exhibit due to ageing and
contamination.