Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSAUDI199590 QUATTRO SPORT V6-2.8L (AAH)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSENGINE SPEED SENSORTESTING AND INSPECTION
1995 Audi 90 Quattro Sport V6-2.8L (AAH)
Engine Speed Sensor: Testing and Inspection
1995 Audi 90 Quattro Sport V6-2.8L (AAH)SECTION Testing and Inspection
CHECKING ENGINE SPEED SENSOR
NOTE:
For functional testing of engine speed sensor, Refer to On-Board Diagnostics, "Read Measuring Value Block" function 08, display group 002. Testing and Inspection
PROCEDURE
- Check that sensor is installed correctly.
- Disconnect gray harness connector.
- Connect multimeter (Fluke 83 or equivalent) to terminals 1 and 2 of connector in connector station, using adapter cable VW 1594 connector test kit.
^ Specified value: approx. 1K ohms
If specified value is NOT obtained:
- Replace engine speed sensor.
If specified value is obtained:
- Connect multi meter to terminals 1 and 3 (Ground) and to terminals 2 and 3 (Ground).
^ Specified value: Infinite ohms in each case (no continuity).
If specified values are not obtained:
- Replace engine speed sensor.
If specified value is obtained:
- Check wiring between sensor connector and ECM.
Wiring Checks
- Connect VAG 1598 test box with VAG 1598/11 adapter harness to ECM wiring harness. Adapter harness is not connected to ECM. Connecting VAG 1598/31 Test Box
- Check shielding by checking for continuity between sensor connector terminal 3 and GND.
^ Specified value: maximum 1.0 ohm
- Check GND wire for continuity between sensor connector terminal 1 and test box socket 1.
^ Specified value: maximum 1.0 ohm
- Check signal wire for continuity between sensor connector terminal 2 and test box socket 2.
^ Specified value: maximum 1.0 ohm
If specified values are not obtained:
- Eliminate short circuit or break in wiring between RPM sensor connector and ECM connector -C-.
Sensor connector ECM connector C terminal
1 5
3 2
Ground 4(GND)
If no malfunction has been found up to this point:
- Inspect teeth on starter gear.
^ The starter must be removed in order to check the gear
- Turn engine slowly and check flywheel for runout and also whether any teeth are broken or damaged; replace if necessary.
If no malfunction was found in all tests so far:
- Replace ECM.
NOTE:
For functional testing of engine speed sensor, Refer to On-Board Diagnostics, "Read Measuring Value Block" function 08, display group 002. Testing and Inspection
PROCEDURE
- Check that sensor is installed correctly.
- Disconnect gray harness connector.
3-Pin Connector:
- Connect multimeter (Fluke 83 or equivalent) to terminals 1 and 2 of connector in connector station, using adapter cable VW 1594 connector test kit.
^ Specified value: approx. 1K ohms
If specified value is NOT obtained:
- Replace engine speed sensor.
If specified value is obtained:
- Connect multi meter to terminals 1 and 3 (Ground) and to terminals 2 and 3 (Ground).
^ Specified value: Infinite ohms in each case (no continuity).
If specified values are not obtained:
- Replace engine speed sensor.
If specified value is obtained:
- Check wiring between sensor connector and ECM.
Wiring Checks
- Connect VAG 1598 test box with VAG 1598/11 adapter harness to ECM wiring harness. Adapter harness is not connected to ECM. Connecting VAG 1598/31 Test Box
3-Pin Connector:
- Check shielding by checking for continuity between sensor connector terminal 3 and GND.
^ Specified value: maximum 1.0 ohm
- Check GND wire for continuity between sensor connector terminal 1 and test box socket 1.
^ Specified value: maximum 1.0 ohm
- Check signal wire for continuity between sensor connector terminal 2 and test box socket 2.
^ Specified value: maximum 1.0 ohm
ECM Harness Connectors:
If specified values are not obtained:
- Eliminate short circuit or break in wiring between RPM sensor connector and ECM connector -C-.
Sensor connector ECM connector C terminal
1 5
3 2
Ground 4(GND)
If no malfunction has been found up to this point:
- Inspect teeth on starter gear.
^ The starter must be removed in order to check the gear
- Turn engine slowly and check flywheel for runout and also whether any teeth are broken or damaged; replace if necessary.
If no malfunction was found in all tests so far:
- Replace ECM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.