1. Connect tester VAG 1551 and dial «01» to select a function «Address word» engine control unit. The engine must be running at idle. The display should show the following information:
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 «002» to select a function «Group 2 display» and press «Q». The display should show the following information:
4. Read the temperature of the incoming air in field 4 of the display.
Continue testing at -48°C
5. Disconnect the four-pin wiring connector from the intake manifold pressure sensor with the intake air temperature sensor (arrow) (engine may stall) (rice. 4.30).
6. Shunt pins 1 and 2 of the wiring connector using the auxiliary wires from the VAG 1594 tester, and observe the readings on the display (pic. 4.34).
Approximately 143°C on the display:
- click «→»;
- click «06» to select a function «Output Completion» and confirm by pressing the button «Q»;
- turn off the ignition;
- Replace the intake manifold pressure sensor with the intake air temperature sensor.
Approximately -48°C on the display:
- click «→»;
- click «06» to select a function «Output Completion» and confirm by pressing the button «Q»;
- turn off the ignition;
- connect the tester VAG 1598/38 to the wiring harness of the engine control unit (on the left side of the engine compartment) (rice. 4.32). the control unit must remain disconnected;
- check the wire between the tester and the connector for an open circuit: tester socket 108 and pin 1, tester socket 85 and pin 2 (rice. 4.33). Set value: max. 1.5 ohm.
- check the wires for a short to positive. Set value: ∞ Ohm.
7. If no fault is found in the wires, then replace the intake manifold pressure sensor with the intake air temperature sensor.
Continue testing at 143°C
8. Disconnect the four-pin wiring connector from the intake manifold pressure sensor with the intake air temperature sensor (arrow) (engine may stall) (rice. 4.30). Approximately -48°C on the display:
- click «→»;
- click «06» to select a function «Output Completion» and confirm by pressing the button «Q»;
- turn off the ignition;
- Replace the intake manifold pressure sensor with the intake air temperature sensor.
Approximately 143°C on the display:
- click «→»;
- click «06» to select a function «Output Completion» and confirm by pressing the button «Q»;
- turn off the ignition;
- connect the tester VAG 1598/38 to the wiring harness of the engine control unit (on the left side of the engine compartment) (rice. 4.32). The control unit must remain disconnected;
- check the wire between the tester and the connector for an open circuit: tester socket 108 and pin 1, tester socket 85 and pin 2 (rice. 4.33). Set value: max. 1.5 ohm.
- additionally check the wires for a short to the positive pole. Set value: ∞ Ohm.
9. If no fault is found in the wires, then replace the intake manifold pressure sensor with the intake air temperature sensor.
Continued test at ambient temperature
10. Remove the intake manifold pressure sensor with the intake air temperature sensor (wiring connector remains connected) (pic. 4.35).
11. Save the temperature value in field 4 of the display.
12. Spray the sensor with coolant while observing the temperature reading. She must go down.
13. Click «→».
14. Click «06» to select a function «Output Completion» and confirm by pressing the button «Q».
15. If specification is not achieved, replace intake manifold pressure sensor with intake air temperature sensor.
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