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. Select the desired group. Click «002» three times for choice «Group 2 display» and confirm by pressing the button «Q». The display should show the following information:
4. Read the engine load value in zone 2 of the display and record this value.
5. Open throttle fully. The motor load value should gradually increase.
6. If the display shows 0% or 99%:
- 0% - open circuit or short to «mass»;
- 99% - short to positive pole.
Continue test if 0% is displayed
7. Disconnect the four-pin wiring connector from the intake manifold pressure sensor with the intake air temperature sensor (arrow) (engine may stall) (pic. 4.30).
8. Shunt pins 3 and 4 of the wiring connector using the auxiliary wires from the VAG 1594 tester and observe the readings on the display (4.31).
If the display is 99%:
- 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.
If the display shows 0%:
- 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) (pic. 4.32). The control unit must remain disconnected;
- check the wire between the tester and the connector for an open circuit: tester socket 98 and pin 3, tester socket 109 and pin 4 (pic. 4.33). Set value: max. 1.5 ohm;
- check the wires for a short on pin 4 on «mass» or to pin 1. Set value: ∞ Ohm.
9. If no fault is found in the wires, then replace the engine control unit.
Continue testing if 99% is displayed
10. Disconnect the four-pin wiring connector from the intake manifold pressure sensor with the intake air temperature sensor (arrow) (engine may stall) (pic. 4.30).
If the display shows 0%:
- 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.
If the display is 99%:
- click «→»;
- click «06» to select a function «Output Completion» and confirm by pressing the button «Q»;
- turn off the ignition;
- remove the cover on the left in the engine compartment, disconnect the wiring connector from the control unit;
- Check for shorted pin 4 of the four-pin harness connector to pin 3 and positive. Set value: ∞ Ohm.
11. If no fault is found in the wires, then replace the engine control unit.
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