Fiat 1998 Marea Service Manual page 183

Marea-Marea
1998 range
When the probe supplies a low voltage level (less than 200 mV) the ECU recognises that the mixture is
lean (lambda » 1) and takes steps to increase the amount of fuel injected. When the probe supplies a
high voltage level (greater than 800 mV) the control unti recognises that the mixture is rich (lambda « 1)
and decreases the quantity of fuel injected.
The lambda probe therefore alters injection times to ensure that the engine operates with a lambda factor
continually fluctuating between 0.980 and 1.020.
Below 300 °C the ceramic material is not active and the probe does not send usable signals. A special
circuit in the control unit blocks loop mixture regulation while the probe is warming up.
To ensure service temperature is reached quickly, the probe is equipped with electrical resistance (4)
supplied by the battery
The probe may be swiftly put out of service by even slight traces of lead in the fuel.
A
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16v
Checking resistance
The heater and probe resistance may be mea-
sured by disconnecting the connector and
connecting an ohmmeter as indicated in the
figure.
Heater resistance = 4.3 - 4.7 ohm
Recovery
Lambda data are ignored (open loop).
Wiring connector
The numbers in boxes indicate correspond-
ing control unit pins.
Engine
Fuel system
10.
( + ) electrode in con-
tact with outside air
(-) electrode in con-
tact with exhaust gas
Ceramic case
Protective pipe
Metal case
Electrical resistant
49