Engine Speed Sensor: Testing and Inspection
Engine Speed (RPM) Sensor, Checking
Function
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.
Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram
Test requirements
- Ground (GND) connections between engine and chassis must be OK.
- Ignition switched off.
Test sequence
- Disconnect gray 3-pin harness connector -1- leading to Engine Speed (RPM) Sensor -G28-.
Checking resistance
- Check sensor resistance between terminals 2 + 3 at connector to sensor.
Specified value: 730 to 1000 Ohms
- Check sensor for short circuit between terminals 1 + 2 as well as 1 + 3.
Specified value: Infinite Ohms
If specified values are obtained:
- Check wires to control module according to wiring diagram.
If specified values are not obtained:
- Replace Engine Speed (RPM) Sensor -G28-.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
Check wires to control module
- Connect test box to control module wiring harness. connect test box for wiring test. Test Box, Connecting For Wiring Test
- Check wires between test box and 3-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 1 + socket 108
Terminal 2 + socket 90
Terminal 3 + socket 82
Wire resistance: max. 1.5 Ohms
- Check wires for short circuit to each other.
Specified value: Infinite Ohms
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 the reference mark and does not mean that the sensor wheel is damaged.
If nothing seems to be wrong with the sensor wheel:
- Replace Motronic Engine Control Module (ECM) -J220-.