Fuel Injector, Checking

Fuel Injector, Checking

The following test procedure is used to diagnose Fuel Injectors N30, N31, N32, N33.

Special tools, testers and auxiliary items required
- Multimeter.
- Diode test lamp (12V).
- Wiring diagram.

Test requirements
- The Fuel Injectors N30, N31, N32, N33 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.

- Observe safety precautions.
- Observe rules for cleanliness.

Test procedure
- Perform a preliminary check to verify the customers complaint. Preliminary Check

Start diagnosis
- Remove the engine cover with air filter.
- Disconnect the Fuel Injector electrical harness connectors.

Checking internal resistance







- Using a multimeter, check the Fuel Injector electrical terminals 1 to 2 for resistance.

Specified value: 12.0 to 20.0 Ohms (at approx. 20 degrees C)

If the specified value was not obtained:
- Replace the malfunctioning Fuel Injector.

If the specified value was obtained:

Checking activation







- Connect a diode test lamp (12V) to the electrical harness connector terminals 1 and 2 of the Fuel Injector to be tested.
- Operate the starter and test the activation of the Fuel Injector.

LED should flicker.
- Switch the ignition off.

If LED does not flicker:

Checking wiring
If the manufacturers test box is being used. Perform the following step.
- Install the test box.

If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) J623.







- Using a Multimeter, check the Fuel Injector electrical harness connector terminals to the Motronic Engine Control Module (ECM) J623 electrical harness connector T60 terminals for an open circuit.







Specified value: 1.5 Ohms Max.

If the specification is not obtained:
- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:
- Erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory.
- 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 not OK:
- Replace the Motronic Engine Control Module (ECM) J623.
- Assembly is performed in the reverse of the removal.

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

1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

End of Diagnosis