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Porsche 944 User Manual

Page 152

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24/28

Fuel System - Electronic Control

944 S/944 S2

Fault, Fault Code

Possible Causes, Elimination, Remarks

Test Point

12:

Control

unit

(knock

computer)

Fault Code

1_33

Ignition timing is retarded 6° in case of this fault.

Replace control unit.

Test Point

13:

Hall signal

Fault Code

1_34

Disconnect plug on cylinder head behind the camshaft drive gear and connect a

three-pin adapter lead (VW 1501) inbetween to check the Hall signal. Connect

oscilloscope positive and negative test leads on terminals 1 and 2 of the adapter

lead. Start the engine.

This signal should be displayed when the Hall system is okay:

Ignition timing will be retarded approximately 6° in all speed ranges, if the DME

control unit recognizes that the Hall signal is missing.

Protective circuit test:

Turn off ignition. Disconnect Hall plug. Start the engine. Idle speed ignition timing

will adjust itself to approximately 4° before TDC (944 S). There must be a certain

load signal from the air flow sensor in case of 944 S2 cars.

Test Point

14:

Control

unit faulty

Fault Code

1_41

Replace control unit.

D 24/28 - 18

DME - Diagnosing/Troubleshooting

Printed In Germany - XXI, 1989