Fiat 1996 Brava Service Manual page 461

Bravo-Brava $
'98 range
16v
Engine
Fuel system
10.
/ / / /~7
ettggSsj
1.
2.
3.
4.
Electrode (+) in con­
tact with the external
air
Electrode (-) in con­
tact with the exhaust
gases
Ceramic casing
Protective pipe
Metal casing
Heating element
When the probe provides a low voltage level (below 200 mV), the control unit recognizes that the mix­
ture strength is weak (lambda »1) and increases the quantity of fuel injected. When the probe provides a
high voltage level (over 800 mV), the control unit recognizes that the mixture strength is rich (lambda «
1) and reduces the quantity of fuel injected.
The Lambda probe thus varies the injection times so that the engine operates with a Lambda coefficient
constantly fluctuating between about 0.980 and 1.020.
For temperatures below 300°C the ceramic material is not active, so the probe does not send usable sig­
nals and a particular circuit present in the control unit blocks the closed loop adjustment of the mixture
strength during the warming up of the probe.
To ensure that operating temperature is quickly reached, the probe has a heating element (4) supplied
by the battery.
The probe can be quickly put out of service by even small quantities of lead in the fuel.
Checking the resistance
The resistance of the heater and probe can be
measured by disconnecting the connector
and connecting an ohmmeter as shown in
the figure.
Heater resistance = 4.3 - 4.7 ohm
Recovery
The Lambda data are ignored (open loop).
Wiring connector
The numbers in boxes indicate the corre­
sponding control unit pins.
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