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.
• Diode test lamp (12 V).
• Wiring diagram.
Test requirements
• The Fuel Injector fuse is OK.
• 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. Refer to the Repair Information.
- Disconnect the Fuel Injector electrical harness connectors from Fuel Injectors (N30, N31, N32, N33, N83 ).
Checking internal resistance
- Using a multimeter, check the Fuel Injector electrical terminals 1 to 2 for resistance.
Specified value: 10.0 to 18.5 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 Diode test lamp (12 V) 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 while engine is cranking.
LED should flicker.
- Switch the ignition OFF.
If LED does not flicker:
- Remove the Fuel Pump Relay (J17).
- Connect a jumper between the Fuel pump relay terminals 30 and 87
- Turn the ignition switch ON.
- Using a test lamp connected to ground, check terminal 1 of the Fuel Injector to be tested. The lamp should be ON.
- If the test lamp did not turn on, locate the open or high resistance in the voltage supply circuit. Fuse S-229 is located between the fuel pump relay and the injectors.
If the voltage supply was OK:
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) ( J220). 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 specified value was Not obtained:
- Check the wiring for an open, high resistance or short to voltage or ground.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring.
If no malfunction is detected in the wiring and If the voltage supply was OK:
- Replace the Motronic Engine Control Module (ECM) (J220). Refer to the Repair Information.
- Install the engine cover. 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.