Fuel Injectors, Checking

Fuel Injectors, Checking

Special tools and equipment
- VAG 1551 Scan Tool or VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/22
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Diode test lamp VAG 1527
- Adapter set VAG 1594
- Wiring diagram

Check conditions
- Engine speed sensor must be OK, checking Testing and Inspection
- Fuel pump relay must be OK
- Fuses 28 and 32 must be OK.

WARNING: Fuel system is under pressure. Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.

Test sequence
- First check the activation of the injectors via Output Diagnostic Test Mode (DTM) Scan Tool Testing and Procedures.

If one or more injectors do not click:

Checking activation and voltage supply

If injectors of cylinder No. 2 or 3 do not click:
- Remove intake manifold upper section.
- Pull connector off injector No. 2 or 3.
- Connect diode test lamp VAG 1527 using auxiliary cables from VAG 1594 to connector contacts of Cyl. 3.
- Operate starter and check the voltage supply for No. 3 cylinder injector.
The LED must flicker
- Repeat check at injector connector for No. 2 cylinder.

If injectors of cylinder No. 1 or 4 do not click:
- Pull connector off injector No. 1 or 4.
- Connect diode test lamp VAG 1527 using auxiliary cables from VAG 1594 to connector contacts of Cyl. 1.
- Operate starter and check voltage supply for No.1 cylinder injector.
The LED must flicker
- Repeat check at injector connector for No. 4 cylinder.
- Switch ignition off.

If the LED does not flicker on any cylinder:







- Connect diode test lamp to Cyl. 1 connector, contact 1 and Ground.
- Initiate Output Diagnostic Test Mode (DTM) again and activate No. 1 cylinder injector.
The LED must light up
- Repeat check at injector connectors for Cyls. 2 through 4.

If the LED does not light up:
- Switch ignition off.
- Check wire between 2 pin connector contact 1 and fuel pump (FP) relay -J17- for open circuit using wiring diagram.
Wire resistance: max. 1.5 Ohm

If the LED flickers on one or several cylinders:







- Connect test box VAG 1598/22 to control module wiring harness.







- Check wiring between test box and connector for open circuit according to wiring diagram.
Injector 1: Contact 2 + socket 73
Injector 2: Contact 2 + socket 80
Injector 3: Contact 2 + socket 58
Injector 4: Contact 2 + socket 65
Wire resistance: Max.1.5 Ohm
- Check additional wires for short to one another.
Specification: Infinite Ohm
- Check wiring for open circuit between injectors (contact 1) using wiring diagram.
Wire resistance: max. 1.5 Ohm
- If no malfunction is found in activation or voltage supply, check resistance of injectors.

Checking resistance of injectors







- Check resistance of injector between contacts.
Specification: 14 to 18 Ohm

NOTE: The resistance figures are valid for approx. 20 degree C. At higher temperatures the resistance figures will increase.

If the specification is not attained:
- Replace faulty injector