Fuel Injectors, Checking
Fuel Injectors, Checking
The following test procedure is used to diagnose all fuel injectors.
Special tools, testers and auxiliary items required
• Multimeter.
• Diode test lamp (12 V).
• Wiring diagram.
Test requirements
• The 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 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 and air intake duct. Refer to the repair information.
- Disconnect the 8 pin connector from the fuel injector assembly harness (located just below and to the right of the electronic throttle motor assembly).
- Turn the ignition switch ON.
- Using a multimeter connected to ground, check terminals 2,4,6,8 for the correct voltage.
Specified value: 22 - 25 V.
- Turn the ignition switch OFF.
If voltage is below specification:
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 2,4,6,8 to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 terminals for an open or short to ground circuit.
Specified values: 1.5 ohms max. for wire continuity, and for circuit to ground check; Infinite or "OL" should be displayed
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 voltage is within specification:
Checking internal resistance
- Using a multimeter, check the Fuel Injector electrical terminals (1 to 2 for N30, 3 to 4 for N31, 5 to 6 for N32 or 7 to 8 for N33 ) for resistance.
Specified value: 1.4 - 2.6 ohms (at approx. 20 °C)
If the specified value was Not obtained:
- Replace the malfunctioning Fuel injector(s). Refer to the repair information.
If the specified value was obtained:
Checking activation and wiring
- Connect a Diode test lamp (12 V) from Battery positive to the injector harness connector terminal (1 for N30, 3 for N31, 5 for N32 or 7 for N33 ) 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 Battery positive or ground.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If no malfunction is found in 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 ] 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.