Porsche 944 Workshop Manual page 148

24/28
Fault, Fault Code
Turn off ignition and reconnect plug if the voltage values have been reached.
Remarks:
Control unit produces replacement values in case of air flow sensor failure
(emergency running program).
Injection signal from nominal air of the idle speed volumetric efficiency control
for idle or a constant injection signal for partial load and full load ranges.
Test Point 6:
Element Activation Menu
Idle speed
control (V)
If pulse cannot be heard, check:
Fault Code
1_22 only S2
Power supply
Connect a voltmeter on terminal 2 and
ground of the disconnected idle speed
control plug.
Turn on ignition.
Display: battery voltage
No display:
Check power supply according to the wiring diagram.
Control signal test
The pulse duty factor in % can be read direct in the "actual value" menu with a
9288 System Tester.
Function test: Switch on electric power consumers with engine running at idle
speed. The pulse duty factor must change and the idle speed must remain
constant.
If not:
D 24/28 - 14
Fuel System - Electronic Control
Possible Causes, Elimination, Remarks
944 S/944 S2
DME - Diagnosing/Troubleshooting
Printed In Germany - XXI, 1989