1. Disconnect the three-pin wiring connector from the crankshaft speed sensor (arrow) (on the thermostat housing) (Fig. 4.38).
2. Connect a multimeter to measure voltage using the leads from the VAG 1594 tester to contacts 1 (positive pole) and 3 ("ground") connector of the crankshaft speed sensor wiring (Fig. 4.39).
3. Turn on the ignition. Specification value: 4.5 V.
4. Turn off the ignition.
5. If there is no voltage, remove the cover on the left in the engine compartment and connect the VAG 1598/31 tester to the wiring harness of the engine control unit (on the left in the engine compartment) (fig. 4.32). The control unit must remain disconnected.
6. Check the wire between the tester and the connector for open circuit: contact 1 and socket 87, contact 2 and socket 82, contact 3 and socket 108 (Fig. 4.39). Specified value: max. 1.5 Ohm.
7. Additionally check for short circuit of wires to each other. Specified value: ∞ Ohm.
8. If no fault is found in the wires and the voltage between contacts 1 and 3 is normal, then replace the crankshaft speed sensor.
9. If no fault is detected in the wires and the voltage between pins 1 and 3 is not normal, then replace the motor control unit.
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