Dodge Sprinter 2006 Manual page 1723

VA
1 - OXYGEN PUMP CELL CIRCUIT
Th e sen sor cell m ea su r es t h e differ en ce bet ween
t h e oxygen con cen t r a t ion in t h e ga s sa m ple ch a m ber
a n d t h e oxygen con cen t r a t ion in t h e ou t side a ir fr om
t h e r efer en ce a ir ch a n n el. A sm a ll volt a ge is gen er-
a t ed a cr oss t h e sen sor, wh ich is pr opor t ion a l t o t h e
a ir-fu el r a t io in t h e sa m ple ch a m ber. At st oich iom et -
r ic r a t io (14.7 lbs. of dr y a ir t o 1 pa r t fu el), t h e cor-
r espon din g open cir cu it volt a ge a t t h e sen sor cell is
450 m V. If t h e st oich iom et r ic r a t io in t h e sa m pler
ch a m ber is h igh er t h a n 1 (excess a ir ) a lower volt a ge
is pr odu ced. If t h e st oich om et r ic r a t io is lower t h a n 1
(in su fficien t a ir ) a h igh er volt a ge is pr odu ced (F ig.
26).
Th e E CM u ses t h is volt a ge sign a l t o det er m in e
h ow a n d wh en t o r u n t h e oxygen pu m p cell. Th e goa l
of t h e E CM is t o m odu la t e t h e pu m pin g cu r r en t
t h r ou gh t h e pu m p cell t o a lwa ys m a in t a in st oich io-
m et r ic a ir-fu el r a t io (14.7 t o 1) in t h e ga s sa m ple
ch a m ber. Wh en st oich iom et r y is r ea ch ed, t h er e is n o
cu r r en t flowin g t o t h e oxygen pu m p.
H igh E xcess Air Mode Wh en t h e exh a u st ga s is t oo
lea n , t h e oxygen con cen t r a t ion in t h e ga s sa m ple
ch a m ber is h igh . Th e sen sor cell m ea su r es t h e differ-
Fig. 26 WIDE BAND OPERATION
2 - SENSOR CELL CIRCUIT
en ce bet ween t h e oxygen con cen t r a t ion s in t h e sa m -
pler ch a m ber a n d t h e r efer en ce a ir ch a n n el. A volt a ge
lower t h a n 450m V is gen er a t ed a cr oss t h e sen sor
cell, wh ich is pr opor t ion a l t o t h e a ir-fu el r a t io in t h e
sa m ple ch a m ber. Th e E CM com pa r es t h e sen sor cell
volt a ge wit h t h e r efer en ce volt a ge (V Ref), wh ich cor-
r espon ds t o t h e st oich iom et r ic poin t volt a ge. Sin ce
sen sor cell volt a ge is lower t h a n V Ref, t h e E CM
det er m in es a lea n con dit ion exist s. Am a m plifier
a pplies a n a ppr opr ia t e volt a ge t o t h e pu m p cell t o
t r a n sfer oxygen fr om t h e ga s sa m ple ch a m ber
Low E xcess Air Mode Wit h low excess a ir m ode,
t h e oxygen con cen t r a t ion in t h e ga s sa m ple ch a m ber
is low. Th e sen sor cell m ea su r es t h e differ en ce
bet ween oxygen con cen t r a t ion s in t h e ga s sa m ple
ch a m ber a n d t h e r efer en ce a ir ch a n n el. A volt a ge
h igh er t h a n 450 m V is gen er a t ed a cr oss t h e sen sor
cell, wh ich is pr opor t ion a l t o t h e a ir-fu el r a t io in t h e
sa m ple ch a m ber. Th e E CM det er m in es a low excess
a ir con dit ion exist s. Th e pola r it y of t h e pu m p cell is
r ever sed a n d so is t h e dir ect ion of t h e cu r r en t flow.
FUEL INJECTION 14 - 47