20V Motronic ECU System

1991 200TQ and 1992-95 S4/S6 with 20V Turbo Engine:

Hall Effect Sensor

The Hall Effect Sensor is used to indicate the position of #1 cylinder when the engine is first started and to determine the injection timing and sequence.

---

On the 1991 200TQ 20V the distributor has a Hall Effect sensor mounted inside.

---

Early 1992 Audi S4 with hall effect sensor mounted in the distributor.

Note the dummy distributor cap that covers the top of the distributor.

---

The 1992-95 S4/S6 have a hall effect sensor that is mounted behind the camshaft gear in front of the engine. The Camshaft gear needs to be removed in order to replace the Hall Effect Camshaft Sensor

---

This Hall Effect Sensor is also used as a reference for the knock sensor operation. The Hall Effect sensor is a semiconductor junction that changes conduction characteristics when exposed to a magnetic field. The Hall Effect Sensor has a metal trigger wheel with a window to expose the sensor to a magnetic field.

NOTE: If the Hall Effect sensor fails, the engine can not be started, but if the hall sensor fails when the engine is running, the engine will keep running and the ECU will use the reference sensor and engine speed sensor, but the ignition timing will be retarded by 6 degrees [1].


Return to 20V ECU System information index

References: [1] Audi of America, Technical service training publication:

"The New 20V Turbo Engine for the Audi 200 Quattro-publication All rights reserved.

Copyright © SJM Autotechnik™ , all rights reserved

Return to Troubleshooting Tips page.

Return to SJM Autotechnik™ main page.