Porsche 1989 944 S2, Workshop Manual

Page: 150 / 167

24/28
Fuel System - Electronic Control 944 S/944 S2
Fault, Fault Code Possible Causes, Elimination, Remarks
Test Point 8:
Oxygen sensor
(V)
(sensor signal)
Fault Code 1_24
Sensor signal test
Sensor voltage can be read direct in the "actual value" menu with a 9288
System Tester.
If not:
Disconnect oxygen sensor plug. Connect a digital display
voltmeter on the sensor end test connection (sensor
voltage signal) and ground.
Start and run engine warm so that the oxygen sensor
reaches its operating temperature. A change in the
voltage signal must be displayed when the mixture is
richer, e.g. by accelerating.
Display on voltmeter:
approx. 150 mV - 900 mV (depending on composition of mixture)
Remarks:
If the control unit recognizes an oxygen) sensor voltage signal of more than
1 V or less than 0.1 V, the control unit will switch over to operation without
oxygen sensor (short or break).
If regulation does not work and the sensor voltage signal is okay, check the
coding of the control unit before replacing the control unit.
Test Point 9
Air temperature
sensor
NTC I ( )
Fault Code 1_25
Intake air temperature can be read direct in the "actual value" menu with a
9288 System Tester.
If not or when a non-plausible value is displayed:
Connect an ohmmeter on terminal 44 and terminal 26 of the disconnected
DME control unit plug.
Display at: 0°C =
15-30°C =
40°C =
4.4-6.8 k
1.4-3.6 k
1-1.3 k
D 24/28 - 16 DME - Diagnosing/Troubleshooting
Printed In Germany - XXI, 1989