Fuel Injectors, Checking
Diagnostic Procedures
Fuel Injectors, Checking
Special tools, testers and auxiliary items required
• Hand multimeter (V.A.G 1526) or Multimeter (V.A.G 1715)
• Voltage tester (V.A.G 1527)
• Test adapter kit (V.A.G 1594)
• Wiring diagram
Test conditions
• Motronic Engine Control Module (ECM) Power Supply Relay (J271) -position 4- must be OK, check:
• Electrical fuel pump relays must be OK.
• Battery voltage (both batteries) must be at least 11.5 Volts.
• All electrical consumers such as, lights and rear window defroster must be switched off.
• For vehicles with automatic transmission, selector lever must be in "P".
• Parking brake must be engaged.
• The Ground (GND) connections between engine and body must be OK.
• Engine Speed (RPM) Sensor must be OK, checking => [ Engine Speed Sensor, Checking ]. Engine Speed Sensor, Checking
• Ignition switched off.
• Fuse -29- for fuel injectors 1 to 12 in right instrument panel fuse holder must be OK:
Right instrument panel fuse holder
Test Sequence
- Remove intake manifold upper part (along with both intake manifold side parts). Refer to Repair Information.
- Remove connector for fuel injectors 1 to 12 ( (N30, N33, N83, N86, N299, N302)).
• Cylinder bank 1 with cylinders 1 through 6 is located at right in direction of travel.
• Cylinder bank 2 with cylinders 7 through 12 is located at left in direction of travel.
Resistance values of fuel injectors, checking
- Test resistance of fuel injectors between terminals. Specification: 14.0 to 16.0 ohms
If specification is not attained:
- Replace faulty fuel injector.
When installing fuel injector, observe the following:
• Replace O-rings on all injectors and lightly moisten with clean engine oil.
• Insert fuel injectors into fuel rail perpendicular and in correct position, and secure them with retaining clips.
• Position fuel rail with secured fuel injectors on intake manifold and apply uniform pressure to press it in.
• The connectors must audibly engage in the injectors when pushed on.
- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
Checking voltage supply
- Connect diode test lamp to connector of fuel injector to be tested terminal 1 + Ground (GND).
- Operate starter and check voltage supply for fuel injectors. LED must light up
- Switch ignition off.
If LED does not light up:
- Check wire between 2-pin connector terminal 1 and corresponding fuse in E-Box (in plenum chamber, right side) for open circuit according to wiring diagram. Wiring resistance: max. 1.5 ohms
- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
Actuation and voltage supply, checking
- Connect diode test lamp to connector terminals 1 + 2 of fuel injector to be checked.
- Operate starter and test activation of corresponding Engine Control Module (ECM) for fuel injector. LED must flicker
- Switch ignition off.
If LED does not flicker:
- Check wires to Engine Control Module according to wiring diagram.
Checking wires to Engine Control Module
Cylinder bank 1
- Connect test box to Engine Control Module (ECM) (J623) wiring harness on connecting test box for wiring test, refer to Repair Information.
Cylinder bank 2
- Connect test box to Engine Control Module (ECM) 2 (J624) wiring harness on connecting test box for wiring test, refer to Repair Information.
Cylinder bank 1 and 2
- Check wires between test box and 2-pin connector for open circuit according to wiring diagram. Wiring resistance: max. 1.5 ohms
Cylinder bank 1
Cylinder bank 2
Cylinder bank 1 and 2
- Check wires for short circuit to B+ and Ground (GND). Specification: infinite ohms
- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
If no malfunction is detected in the wiring, replace the engine control module. Refer to Repair Information.