Audi Workshop Service and Repair Manuals

The metering unit (quantity adjuster) is an electromagnetic swivelling positioner which is controlled by the control unit via a directed duty cycle (on-off ratio). The eccentric shaft on the metering unit moves the modulating piston on the high pressure piston and thereby regulates the quantity of fuel injected.

The modulating piston movement sender informs the control unit of the position of the modulating piston, thereby indicating the quantity of fuel injected.

• ‒ Read measured value block, Display Group 01, engine at idling speed

• ‒ Check display in display zone 4 (coolant temperature).

Continue with check when coolant temperature is attained.

• ‒ Switch off any electrical consumers that may be on (air conditioner, rear window heater, lights etc.).

• ‒ Check display in display zone 3 (voltage supplied from modulating piston movement sender).

If the specification is not obtained:

• ‒ Replace injection pump.

Electrical check of modulating piston movement sender (G149) and quantity adjuster (N146)

• ‒ Switch off ignition.
• ‒ Disconnect connector for sender=>Fitting locations overview, Page 23-4.
• ‒ Connect hand-held multimeter (resistance test range) between the following contacts on the injection pump connector:

→ Testing wiring connections on vehicles with 8-pin connector.

→ Testing wiring connections on vehicles with 10-pin connector.

If the specifications are not obtained:

• ‒ Replace injection pump.

Testing current supply and wiring connections

• ‒ Switch off ignition.
• ‒ Disconnect connector for sender=>Fitting locations overview, Page 23-4.
• ‒ Switch ignition on.

• ‒ Connect hand-held multimeter (voltage test range) between the following contacts on the wiring harness connector:

→ Measuring voltage on vehicles with 8-pin connector.

→ Measuring voltage on vehicles with 10-pin connector.

If the specifications are not obtained:

• ‒ Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
  => Page 23-47.

The following wiring connections are to be checked for open circuits and/or short to positive or negative.

→ Testing wiring connections on vehicles with 8-pin connector.

→ Testing wiring connections on vehicles with 10-pin connector.

• ‒ Rectify any open/short circuit as necessary.