Engine control module (contd.)
The engine control module is continuously supplied
with power (+30 circuit) and loses adapted values
and diagnostic trouble codes stored in its memory if
this power circuit fails.
The ECM is adjusted for a voltage between 8 and 16
V during driving.
Switching on the ignition activates the engine control
module and causes the CHECK ENGINE lamp (MIL)
to light up and stay on as an indication that all sys-
tems are OK. The engine control module then waits
for pulses from the crankshaft position sensor.
The main measured quantity for fuel injection comes
from the manifold absolute pressure sensor.
There are substitute functions for all sensors apart
from the crankshaft position sensor.
When the ignition is switched off, ail the sensors sup-
plied with 5 V are activated for 15 minutes. During
this time, diagnostics with an ISAT scan tool can also
be performed. After 15 minutes only the memory, in
which adapted values are stored, remains activated.
Adaptation is important for performance, driveability,
fuel consumption and emission control. The control
module should therefore not be removed unneces-
sarily or have its power supply disconnected in any
other way.
Technical Description 27
Important
There is a specific control module for each engineĀ·
version. Fitting the wrong control module will result
in driveability problems or damage to the power
train.
Saab 9000
I
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