Engine Speed (RPM) Sensor, Checking

Engine Speed (RPM) 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.

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

Requirements







- The respective fuses of Diesel-Direct fuel injection system must be OK:
- Battery voltage must be at least 11.5 volts.
- All electrical consumers such as, lights and rear window defroster must be switched off.
- For vehicles with automatic transmission, selector lever must be in -P-.
- Parking brake must be engaged.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Ignition is switched off.

Test sequence







- Disconnect harness connector -2- of Engine Speed (RPM) Sensor -G28-..







- Measure sensor resistance between terminals 1 + 2 at connector to sensor.
Specified value: 450 to 650 Ohms.
- Check wires on connector to sensor for short circuit to shielding.

Terminal 1 + 3
Terminal 2 + 3

Specified value: Infinite Ohms

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

If specified value is obtained:
- Check wires to Engine Control Module (ECM) according to wiring diagram.

Check wires to control module
- Connect test box (1598/42) to Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- wiring harness using adapter cable (V.A.G 1598/39-1), connecting test box for wiring test. Test Box, Connecting For Wiring Test







- Check wires between test box and 3-pin connector for open circuits according to wiring diagram.

Terminal 1 + socket 58
Terminal 2 + socket 43
Terminal 3 + socket 43

Wire resistance: max. 1.5 Ohms

- Check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinite Ohms

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

If no malfunction can be detected:
- Replace Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-.