Engine Speed (RPM) Sensor -G28- Checking

Engine Speed Sensor, Checking
The engine speed (RPM) sensor -G28- detects engine speed and reference marks. Without an engine speed signal, the engine will not start. If the engine speed signal fails while the engine is running, the engine will stop immediately.

Special tools and equipment
- VAG1551 scan tool (or VAG1552 mobile scan tool) with VAG1551/3B cable
- VAG1598/31 test box
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test sequence







- Disconnect gray 3-pin harness connector (arrow) leading to the engine speed (RPM) sensor.







- Measure resistance of sensor between terminals 2 + 3 at connector to sensor.
Specification: 480 to 1000 Ohms
- Check sensor for shorts between terminals 1 + 2 and 1 + 3. Specification: Infinity Ohms

If specified values are not obtained:
- Replace engine speed (RPM) sensor -G28-
- Check DTC memory, repair any malfunctions and then erase DTC memory.

If no DTC is found on sensor:







- Connect VAG1598/31 test box to control module wiring harness. Engine Control Module (ECM) is not connected.
- Check wires between test box and 3-pin connector for open circuits according to wiring diagram.

Terminal 1 + socket 108
Terminal 2 + socket 90
Terminal 3 + socket 82

Wire resistance: max: 1.5 Ohms







- Also check wires for short circuit to each other.

If no malfunctions are found in wires:
- Remove sensor and check sensor wheel for secure fit, damage, and run-out.


NOTE: There is a larger-sized gap on the sensor wheel. This gap is a reference mark, not damage.


If nothing seems to be wrong with the sensor wheel:
- Replace Engine Control Module (ECM).

After successful repair:
- Read readiness code. If DTC memory was erased or the Engine Control Module (ECM) was disconnected from the continuous B+ supply, the readiness code must be re-generated. Refer to Monitors, Trip and/or Drive Cycle (Readiness Codes)/Reading Readiness Code. Testing and Inspection Refer to Monitors, Trip and/or Drive Cycle (Readiness Codes)/Generating Readiness Code. Testing and Inspection