Checking the inlet air temperature sensor (VW Lt 2d)

1. Connect the VAG 1551 tester and, by entering "01" "Engine electronics", select the engine control unit. The engine should be idling. The display should show the following information:

• Fast data exchange HELP
• Dial function XX

2. Press "08" to select the "Read Block of Measured Values" function and confirm with the "Q" button. The display should show the following information:

• Reading the measured value block HELP
• Enter group number XXX

3. Press "002" to select the "Display Group 002" function and press "Q". The display should show the following information:

Reading block of measured values 2 → 1 2 3 4

4. Read the incoming air temperature value in field 4 of the display.

5. Remove the intake air temperature sensor 1 (figure 2.81).



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6. Blow cold air onto the sensor and monitor the temperature reading. It should go down.

7. Click "→".

8. Press "06" to select the "Complete Output" function and confirm by pressing the "Q" button.

9. Turn off the ignition.

10. If the temperature value in field 4 does not drop, connect the VAG 1598/26 tester.



11. Disconnect the 2-pin connector from the intake air temperature sensor (arrow) (figure 2.82).



12. Check the wires between the tester and the 2-pin connector for open circuit using the wiring diagram (figure 2.83): contact 2 and socket 16 (blue). contact 1 and socket 9 (blue). Wire resistance: 1.5 ohms.

13. Check the wire between the tester and pin 2 of the connector for a short circuit with the wire of pin 1 and to ground, using the wiring diagram: pin 2 and socket 9 (blue). Specified value: ∞ Ohms.




14. Also check the short circuit of the wires to the positive terminal of the battery. Set value: ∞ Ohm.

15. If there is no damage to the wires, check the resistance between contacts 1 and 2 of the inlet air temperature sensor. The specified values are given in Table 2.7.

Table 2.7. Specified resistance values between the contacts of the inlet air temperature sensor

Temperature	Resistance	Temperature	Resistance
10°C	9.21-10.15 kOhm	50°C	1.68-1.85 kOhm
20°C	5.77-6.36 kOhm	60°C	1.16-1.28 kOhm
30°C	3.71-4.10 kOhm	70°C	820-900 Ohm
40°C	2.50-2.73 kOhm	80°C	590-650 Ohm