With Generic Scan Tool

Engine Speed (RPM) Sensor G28 , checking

Note:
- Use only gold-plated terminals when servicing terminals in the electrical harness connector of the Engine Speed (RPM) Sensor G28.

Special tools, testers and auxiliary items required
- Multimeter
- Wiring diagram

Test requirements
- The Motronic Engine Control Module (ECM) J220 fuses OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position "P" or "N".
- A/C switched off.
- Ground (GND) connections between engine/transmission/chassis OK.
- Ignition switched off.

Function
The Engine Speed (RPM) Sensor G28 detects RPM 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.

Test procedure

- Perform a preliminary check to verify the customers complaint. Service and Repair

Start diagnosis

Function test

- Connect the scan tool.

- Switch the ignition on.

- Using the scan tool, check the engine speed:

Diagnostic text Specified value
Engine rotations per minute (RPM) Idle speed

- End diagnosis and switch ignition off.

If the specified value was not obtained:

Checking internal resistance






- Disconnect the gray Engine Speed (RPM) Sensor G28 electrical harness connector -1-.






- Using a multimeter, check the Engine Speed (RPM) Sensor G28 terminals 2 to 3 for resistance.

Specified value: 730 to 1000 Ohms (at approx. 20�C)

- Check Engine Speed (RPM) Sensor G28 terminals 1 to 2 and 1 to 3 for short circuits.

Specified value: infinity

If any of the specified values are not obtained:

- Replace the Engine Speed (RPM) Sensor G28.

If the specified values are obtained:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box Test Box 105 Pin VAG1598/31.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) J220. Service and Repair






- Using a Multimeter, check the Engine Speed (RPM) Sensor G28 electrical harness connector terminals to the Motronic Engine Control Module (ECM) J220 electrical harness connector T121 terminals for an open circuit.






Specified value: 1.5 Ohms Max.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

- Check the electrical harness connector for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Remove the Engine Speed (RPM) Sensor G28 and check the sensor wheel for proper seating, damage and run-out.

If the sensor wheel is OK:

- Erase the DTC memory. Diagnostic Mode 4: Reset/Erase Diagnostic Data

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

- Replace the MFI Engine Control Module (ECM) J220. Service and Repair

- Assembly is performed in the reverse of the removal.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.

End diagnosis