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Engine Speed Sensor, Checking






Diagnostic Procedures

Engine Speed 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.

Special tools, testers and auxiliary items required

• Multimeter (VAG1526) or Multimeter (VAG1715)

• Connector test kit (VAG1594)

• Wiring diagram

Test Prerequisites

• Fuses in E-box (plenum chamber, left) must be OK:





• Battery voltage must be at least 11.5 volts.

• Ground (GND) connections between engine and chassis must be OK.

• Ignition is switched off.

Test Sequence

- Connect test box ((VAG1598/42)) to Engine Control Module (ECM) (J623) wiring harness using adapter cable ((VAG1598/39-1)) , connecting test box for wiring test.

- Measure resistance of sensor between sockets 43 + 58 of test box.

Specified value: 530 to 650 ohms

- Check wires for short circuit to shielding between test box sockets.

Socket 57+43

Socket 57+58

Specified value: infinite ohms

If specified values are not obtained:

- Replace Engine Speed (RPM) Sensor (G28) and wiring harness for Engine Speed (RPM) Sensor (G28).

- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

If specified values are obtained, check Control Module Wires.

Control Module Wires, Checking

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

- Check wires between test box and 2-pin connector for open circuit according to wiring diagram.

Terminal 1+socket 58

Terminal 2+socket 43

Wire resistance: max. 1.5ohms

- Also 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 Engine Control Module (ECM) (J623) --> [ Engine Control Modules, Replacing ] Engine Control Modules, Replacing.
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