Fuel Injector, Checking

Diagnostic Procedures

Fuel Injector, Checking

Test requirements

• Multimeter

• 12 V Diode test lamp.

• Wiring diagram.

Test requirements

• The Fuel Injectors (N30, N31, N32, N33, N83, N84) fuses OK.





• The Engine Speed (RPM) Sensor (G28) OK, checking.

• 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 connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Observe safety precautions. Refer to => [ Safety Precautions ] Safety Precautions

- Observe Clean Working Conditions. Refer to => [ Clean Working Conditions ] Clean Working Conditions

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

Start diagnosis

- Disconnect the fuel injector electrical harness connectors from Fuel Injectors (N30, N31, N32, N33, N83, N84).

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° C)

If the specified value was not obtained:

- Replace the malfunctioning fuel injector. Refer to the Repair Information.

If the specified value was obtained:

Checking activation and wiring

- Connect a 12 V Diode test lamp 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:

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). Refer to the Repair Information.

- Using a multimeter, check the fuel injector electrical harness connector terminals to the Motronic Engine Control Module (ECM) (J220) 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 an open, high resistance or short circuit to voltage or ground.

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

- If necessary, repair the faulty wiring connection.

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

- Perform a road test to verify repair.

If the DTC does not return:

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

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

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to the Repair Information.

- 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. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.