Oxygen Sensor; Intake Air Temperature Sensor - Porsche 944 Workshop Manual

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Fault, Fault Code
Test Point 8:
Oxygen sensor
M
(sensor signal)
Fault Code 1 24
Test Point 9
Air temperature sensor
NTC I (Q)
Fault Code 1 25
D 24/28- 16
Fuel System - Electronic Control 944 S/944 S2
Possible Causes, Elimination, Remarks
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 connec-
tion (sensor voltage signal) and ground.
Start and run engine warm so that the oxygen sen-
sor reaches its operating temperature. A change in
the voltage signal must be displayed when the mix-
ture 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.
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 discon-
nected DME control unit plug.
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DME Diagnosing/Troubleshooting
Printed in Germany- XXI, 1989