Porsche 928 Workshop Manual page 70

928
Maintenance, Self-diagnosis
03
a
It must be possible to measure the battery volt-
age between terminal 2 (positive) and terminal
4 (ground) of the disconnected air-flow sensor
Plug.
123456
If the battery voltage display does not appear,
check the cable harness and plug connections
with reference to the circuit diagram.
Functional check of the hot-wire
signal
Plug the connector into the air-flow senor.
Remove LH relay (XXV) and press terminal 30
and terminal 67 into the relay socket.
It must be possible to measure a voltage be-
tween terminals 6 and 7 on the disconnected
LH control unit plug.
Display: = 1.5 V 1.6 V
Blow onto the hot-wire in the air-flow sensor
and observe the voltmeter.
Display: = 1.5 V - 5 V
Functional check of the hot-wire
self-cleaning process
Allow the engine to run with integrated, con-
nected air-flow sensor.
Condition:
Engine temperature > 140°F
Increase speed to above 2000 rpm.
Turn off the engine, i.e. ignition off. After
approx. 4 seconds, the hot-wire must glow for
approx. 1 second (self-cleaning function).
a
Troubla-shooting
03 - 23
Printed in Germany - XX, 1988