Engine Speed (RPM) Sensor -G28-, Checking
Engine Speed (RPM) Sensor -G28-, Checking
NOTE: The engine speed sensor is an engine speed and reference mark sensor. The engine cannot be started without a signal from the RPM sensor -G28-. If the engine is running it stops immediately in the absence of a signal from -G28-.
Work sequence
- Before checking, ensure proper installation and tight fit of sensor.
- Check speed sensor wheel for chips and damage.
- Disconnect connector of engine speed sensor (identification: gray connector).
- Connect portable multimeter V.A.G 1526 (resistance measurement) with test lead from V.A.G 1594 to contacts 2 and 3 of engine speed sensor connector.
Specification: approx. 730...1000 Ohms
NOTE:
- Resistance value of engine speed sensor is referenced to a temperature of 20 degree C.
- The resistance increases with increasing temperature.
If reading does not match specification:
- Replace engine speed sensor.
If reading matches specification:
- Connect portable multimeter V.A.G 1526 for resistance measurement between contacts 2 and 1 (Ground, screen) as well as to contacts 3 and 1 (Ground, screen).
Specification: infinity Ohms in each case (no continuity)
If reading does not match specification:
- Replace engine speed sensor.
If reading matches specification:
- Check wiring between sensor connector and engine control module as follows:
Wiring between engine speed sensor and engine control module
- Connect test box V.A.G 1598/31 at wiring harness to engine control module. Actual engine control module is not to be connected.
- Check wiring from 3-pin connector (sensor connector)...
- ... to engine control module for open circuit and short to positive/Ground.
3-pin connector at wiring Test box V.A.G 1598/31,
harness,socket socket
1 (screen) 108
2 (Ground wire) 90
3 (signal wire) 82
Resistance: max. 1.5 Ohm
- Eliminate open circuit in wiring/short circuit if necessary.
If no fault is found in wiring:
- Slowly crank engine and check concentricity/tight fit of sensor wheel.
If none of the checks reveals a fault:
- Replace engine control module.