Engine Speed (RPM) Sensor, Checking

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
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test requirements







The respective fuses of Motronic Engine Control Module (ECM) -J220- must be OK.







- Fuses -1, 2, 3, 4 and 7- in protective housing (plenum chamber, left) must be OK.
- Battery voltage must be at least 11.5 Volts.
- All electrical consumers such as, for example, lights and rear window defroster must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.

Test sequence
- Remove intake air hose between Mass Air Flow (MAF) sensor and throttle valve control module, item 1 .







- Disconnect 3-pin connector from Engine Speed (RPM) Sensor -G28-.

Checking voltage supply and wiring to control module







- Connect multimeter between terminal 1 (B+) and 3 (Ground -GND-) for voltage measurement.
- Switch ignition on.
Specified value: at least 4.5 V
- Switch ignition off.

If there is no voltage:
- 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 for open circuit according to wiring diagram.
Terminal 1 + socket 98
Terminal 2 + socket 82
Terminal 3 + socket 90
Wire resistance: max. 1.5 Ohms

- Also check wires for short circuit to each other.
Specified value: Infinity Ohms

If no malfunctions are found in the wires and there was voltage between terminals 1 + 3:
- 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 Engine Speed (RPM) Sensor -G28-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If no malfunctions are found in wires and there was no voltage between terminals 1 + 3:
- Replace Motronic Engine Control Module (ECM) -J220-.