Porsche 1989 944 S2, Workshop Manual

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944 S/944 S2 Fuel System - Electronic Control
24/28
Fault, Fault Code Possible Causes, Elimination, Remarks
Test
Point 5a:
Air flow
sensor
(V/ )
Fault
Code
1_21
The ratio between Up (potentiometer voltage) and Uv (power supply voltage) can
be read in the "actual value" menu with a 9288 System Tester.
When opening the air flow sensor plate the ratio must be about 0.0 to 1. If not:
a) Power supply voltage
Connect a voltmeter on terminal 3 and terminal 4 of the disconnected air flow
sensor plug with help of test leads. Turn on ignition.
Display: 5 +- 0.3 volts
Test
Point
5b:
b) Voltage drop on air flow sensor plate potentiometer (V)
Take off air cleaner connecting hose. Connect pin 3 of the disconnected air flow
sensor plug with air flow sensor plug terminal 3 and pin 4 with air flow sensor plug
terminal 4 with help of test leads.
Connect a voltmeter on air flow sensor terminal 2 and terminal 4 (turn on ignition).
Display: approx. 250 - 260 m V
It must be possible to move the air flow sensor plate easily and without hesitation.
Observe the voltmeter's display at the same time. Voltage jump of voltage drop
should not be observed while the air flow sensor plate is opening or closing.
Display with air flow sensor prate in full load position:
approx. 4.60 volts.
DME - Diagnosing/Troubleshooting
Printed In Germany - XXIV, 1991
D 24/28 - 13