2. Click «08» to select a function «Reading a block of measured values» and confirm by pressing the button «Q». The display should show the following information:
3. Click «001» to select a function «Group 1 display» and press «Q». The display should show the following information:
4. Read the temperature of the incoming air in field 2 of the display.
11 If the displayed temperature is very different from the ambient temperature, check the resistance of the sensor wiring. Group 0 display: 125 units = 20°C, 25 units = 85°C.
Continue testing at 240 or -50°C
5. Disconnect the four-pin wiring connector 1 from the coolant temperature sensor (pic. 5.48).
6. Bridge pins 1 and 3 of the wiring connector using the auxiliary wires from the VAG 1594 tester and observe the readings on the display.
7. Display shows 0 or 130°C: Replace the coolant temperature sensor.
8. Display 240 or -50°C:
- click «→»;
- click «06» to select a function «Output Completion» and confirm by pressing the button «Q»;
- turn off the ignition;
- connect the tester VAG 1598/18 to the wiring harness of the engine control unit;
- check the wire between the tester and the connector for an open circuit: socket 42 of the tester and pin 4 of the four-pin wiring connector (rice. 5.45). Set value: max. 1.5 ohm.
- check the wires for a short to positive. Set value: ∞ Ohm.
- check the wire between the tester and the connector for an open circuit: socket 17 of the tester and pin 1 of the four-pin wiring connector. Set value: max. 1.5 ohm.
9. If no fault is found in the wires, then replace the engine control unit.
Continue testing at 0 or 130°C
10. Disconnect 4-pin harness connector 1 from coolant temperature sensor 2 (pic. 5.49).
11. Display shows 240 or -50 'C: replace the coolant temperature sensor.
12. Display 0 or 130°C:
- click "→"
- click «06» to select a function «Output Completion» and confirm by pressing the button «Q»;
- turn off the ignition;
- disconnect the wiring connector from the engine control unit;
- check the wire to pin 3 of the four-pin engine control unit wiring connector for a short to pin 1 of the wire and to «mass». Set value: ∞ Ohm.
13. If no fault is found in the wires, then replace the engine control unit.
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