Fuel Injectors, Checking

Observe all safety precautions: SAFETY PRECAUTIONS 

View clean working conditions: CLEAN WORKING CONDITIONS 

Prior to repair work, perform a preliminary check to verify the condition. Refer to PRELIMINARY CHECK .

Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.

For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.

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

Special tools and workshop equipment required 

• multimeter.
• 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.

Start diagnosis 

-- Remove the engine cover.

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

Checking internal resistance 

-- Using a multimeter, check the Fuel Injector -- terminals 1 to 2 for resistance.

Specified value: 178 K to 184 K Ω (at approx. 20° C)

If the specified value was Not obtained:

-- Replace the malfunctioning Fuel Injector --.

If the specified value was obtained:

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 a short to ground or voltage, high resistance or an open circuit.

Component	Fuel Injector -- electrical harness connector terminals	Motronic Engine Control Module (ECM) -J623- electrical connector T60 terminals or test box sockets
Cylinder 1 Fuel Injector -N30-	1	46
	2	31
Cylinder 2 Fuel Injector -N31-	1	2
	2	17
Cylinder 3 Fuel Injector -N32-	1	1
	2	16
Cylinder 4 Fuel Injector -N33-	1	47
	2	32

Specified value: 1.5 Ω Max.

If the specified value was Not obtained:

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

-- 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.

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 .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .