234 Fault diagnosis
Low boost press~re
(contd.)
2 Investigate the cause of the fault
In the following it will be determined whether the fault
is a control fault or a basic engine/turbo fault.
- Disconnect the air hose marked
"W"
from
the
boost pressure control valve, checking at the
same time that it is connected to the wastegate.
- Drive the car.
When driving at wide open throttle from low engine
rpm, the pressure switch should open before
3000 rpm is attained.
Does the switch open?
I
YES
I
Continue with point 3.
I
NO
I
Check and,
if
necessary, rectify the following:
•
Leakage
in the intake system between tur-
bo unit and throttle body (e.g. in the bypass
valve).
• Clogged air cleaner.
• Turbo unit fault.
• Incorrectly adjusted basic boost pressure.
• Basic engine fault.
• Clogged exhaust system.
Saab9000
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