2. Press "08" to select the "Read measured value block" function and confirm by pressing the "Q" button. The display should show the following information:
3. Select the desired group. Press "002" three times to select "Display Group 2" and confirm with the "Q" button. The display should show the following information:
4. Read the engine load value in display area 2 and record this value.
5. Open the throttle valve fully. The engine load value should gradually increase.
6. If the display shows 0% or 99%:
- 0% - chain break or shorting to "ground";
- 99% - short circuit to positive pole.
Continue checking if 0% is displayed
7. Disconnect the four-pin wiring connector from the intake manifold pressure sensor with intake air temperature sensor (arrow) (the engine may stall) (Fig. 4.30).
8. Shunt contacts 3 and 4 of the wiring connector using auxiliary wires from the VAG 1594 tester and observe the readings on the display (4.31).
If the display shows 99%:
- press "→";
- press "06" to select the "Complete Output" function and confirm by pressing the "Q" button;
- turn off the ignition;
- replace the intake manifold pressure sensor with the intake air temperature sensor.
If the display shows 0%:
- press "→";
- press "06" to select the "Complete Output" function and confirm by pressing the "Q" button;
- turn off the ignition;
- connect the VAG 1598/38 tester to the engine control unit wiring harness (on the left in the engine compartment) (Fig. 4.32). The control unit must remain disconnected;
- check the wire between the tester and the connector for open circuit: tester socket 98 and contact 3, tester socket 109 and contact 4 (Fig. 4.33). Specified value: max. 1.5 Ohm;
- check the wires for short circuit of contact 4 to ground or to contact 1. Specified value: ∞ Ohm.
9. If no fault is found in the wires, then replace the engine control unit.
Continue checking if 99% is displayed
10. Disconnect the four-pin wiring connector from the intake manifold pressure sensor with intake air temperature sensor (arrow) (the engine may stall) (Fig. 4.30).
If the display shows 0%:
- press "→";
- press "06" to select the "Complete Output" function and confirm by pressing the "Q" button;
- turn off the ignition;
- replace the intake manifold pressure sensor with the intake air temperature sensor.
If the display shows 99%:
- press "→";
- press "06" to select the "Complete Output" function and confirm by pressing the "Q" button;
- turn off the ignition;
- remove the cover on the left in the engine compartment, disconnect the wiring connector from the control unit;
- check for shorting of pin 4 of the four-pin wiring connector to pin 3 and to the positive pole. Specified value: ∞ Ohms.
11. If no fault is found in the wires, then replace the engine control unit.
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