Fuel Injector, Checking

Fuel Injector, Checking

This procedure is used to diagnose Fuel Injectors (N30, N31, N32, N33, N83).

Special tools, testers and auxiliary items required

• Multimeter

• Low current draw voltage tester ()

• wiring diagrams

Test requirements

• Fuses for Fuel Injectors (N30, N31, N32, N33, N83) OK.

• Engine Speed (RPM) Sensor (G28) 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.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

- Pull engine cover out of first mount at front arrow 1, then at right rear arrow 2 and finally at left rear arrow 3.





- Disconnect the electrical harness connectors on Fuel Injectors.

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

Checking resistances

- Using a multimeter () check Fuel Injector terminals 1+2 for resistance





Specified value: 12.0 to 20.0 ohms (at approx. 20° C)

If the specification is not obtained:

- Replace the malfunctioning fuel Injector.

Checking activation and wires

- Using low current voltage tester , check the fuel Injector electrical connector for voltage.





- Operate starter and test activation for Fuel Injector.

LED should flicker.

- Switch ignition off.

If LED does not flicker:

- Using the Multimeter, check the following wiring connection(s) for an open circuit.









Specified resistance 1.5 ohms max.

If the specified value is not obtained:

- Repair the wiring connection.

If no malfunctions are found in the wiring:

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase 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. Refer to => [ Readiness Code ] Readiness Code.

- End diagnosis.

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

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.

- 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. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code, Setting ] Readiness Code, Setting.

End of Diagnosis.