Porsche 928 Workshop Manual page 588

929 s4
928 GT Electronic Fuel Injection
24
Fault, Fault Code
Possible Causes. Elimination. Remarks
Test point 1
Power supply voltage
too high /too low
LH control unit
Fault code l-1 1
If the power supply drops below 10 V or rises above q6 V, this is
stored in the fault memory.
Check voltage at regulator; check plug connection and terminals for
firm contact and
freedom from corrosion.
Test
point 2
Idle speed contact (0)
Short to ground
Fault code l-12
Check by means of circuit input test with 9288 system tester, or
9268 tester
Select the test step and depress the accelerator pedal.
9268 display: Idle speed contact closed
Idle speed contact open
9268 display:
1332 (idle speed contact closed)
0000 (idle speed contact open).
No display:
Disconnect plugs from EZK and LH control unit.
Connect ohmmeter betweern terminals 2 and 5. using test leads.
Display:
Throttle valve closed < 10R
Throttle valve opening angle >l"=mB
The idle speed contact must open immediately
pen circuit: Ignition timing at idle speed approx. 20" CS (crankshaft
rotation).
No fuel cutoff when coasting, higher idle speed.
Short circuit:
Fuel cutoff as engine runs up, once
after every engine start. Ignition timing approx. 10
retarded.
a
LH-Diagnosisflroubleshooting
Prlnted in Germany - Xxy, 1990
D 24- 11