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944 S/944 S2 Fuel System - Electronic Control
24/28
Fault, Fault Code Possible Causes, Elimination, Remarks
Connect two-pin DME test lead (Bosch No. 1 684 463 093) between the speed
control and plug.
Connect and adjust engine tester to supplied operating instructions.
Make sure that electric lead connections do not have contact with vehicle ground
(danger of short).
Displayed with the engine running:
Frequency: approx. 100 Hz.
Replace the idle speed control it the pulse cannot be heard in spite of correct
power supply and received signal.
Test Point
7
Oxygen
regulation
on stop
Fault Code
1_23
Oxygen regulation cannot work in its regulating range in case at disturbances in
air/fuel mixture; for example: too lean because of excessive air or too rich
because of a sticking fuel injector. It then moves against the stop.
Test 1:
Check CO level with the engine running and CO
tester connected (between 0.4 and 1.2 %).
too lean:
Check intake system for leaks
(Test Point 19).
too rich:
Check system pressure (Test Point 18).
Check fuel injectors for leaks (Test Point 18).
DME - Diagnosing/Troubleshooting
Printed In Germany - XXI, 1989
D 24/28 - 15