Fuel Injectors, Checking

Diagnostic Procedures

Fuel Injectors, Checking

The following test procedure is used to diagnose all fuel injectors.

Special tools, testers and auxiliary items required

• Multimeter.

• 12V diode test lamp

• Wiring diagram.

Test requirements

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

• The Engine Speed (RPM) Sensor (G28) is 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 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. Refer to => [ Preliminary Check ] Preliminary Check

Start diagnosis

- Remove the engine cover with air filter. Refer to the repair information.

- Disconnect the Fuel Injector electrical harness connectors from Fuel Injectors (N30, N31, N32, N33)- arrows -.





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 12V 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) (J623) electrical harness connector T60 terminals for an open circuit.





Specified value: 1.5 ohms Max.

If the specified value was Not obtained:

- Check the wiring for an open, high resistance or short to ground.

- 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:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to the repair information.

- Install the engine cover with air filter. Refer to the repair information.

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 ] Scan Tool Testing and Procedures.

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

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