Direct Petrol Injection System with Bosch Motronic MED 7 - Volkspage

Broadband lambda probe (G39)
The broadband lambda probe is screwed into
the exhaust manifold upstream of the catalyst
and is used to determine the residual oxygen
fraction in the exhaust gas.
Broadband lambda probe
(G39)
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Signal utilisation
The broadband lambda probe can be used to
define the air/fuel ratio accurately, and even
ratios deviating from lambda = 1.
mA
3.0
Lambda = 1
As a result, a lean lambda of 1.55 can be set in
homogeneous lean charge mode. In stratified
charge mode, the lambda is calculated because
broadband lambda probes are too inaccurate in
this range.
Taking this signal as a basis, the engine control
unit calculates the actual lambda value and
commences lambda control when deviations
from the target lambda value are detected. The
lambda is controlled via the injection quantity.
Pump current l p
2.0
1.0
0
-1.0
-2.0
0.7 1.0 1.3 1.6 1.9 2.2 2.5 3.0
Air quotientλ
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Signal failure strategies
If the signal from the lambda probe fails, the
system adopts an injection quantity precontrol
strategy rather than a lambda control strategy.
In addition, lambda adaption is disabled and the
activated charcoal canister system goes into
emergency running mode.
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