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Porsche 944 User Manual

Page 150

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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