Audi Workshop Service and Repair Manuals

Procedure before opening high-pressure section of injection system t  The injection system consists of a high-pressure section (maximum approx. 120 bar) and a low-pressure section (approx. 6 bar). t  Before removing a component in the high-pressure section of the injection system, the fuel pressure in the high-pressure section must be reduced to a residual pressure of approx. 6 bar; follow the procedure outlined below. Special tools and workshop equipment required

t  Removal wedge -3409- t  Vehicle diagnostic, testing and information system -VAS 5051B-

Procedure –  With ignition switched off, connect vehicle diagnostic, testing and information system -VAS 5051B- with diagnosis lead to diagnosis connection. –  Start engine and run at idling speed.

Display on -VAS 5051B-: –  Select Vehicle self-diagnosis from the list -item 1-.

Display on -VAS 5051B-: –  From menu -1-, select “Self-diagnosis” system and press → key to continue.

Display on -VAS 5051B-: –  From menu -1-, select vehicle system “Engine electronics” and press → key to continue.

Display on -VAS 5051B-: –  From menu -1-, select function “Measured values” and press → key to continue.

Display on -VAS 5051B-: –  From menu -1-, select measured value “fuel pressure” and press → key to continue.

Display on -VAS 5051B-: –  Check display -2- indicating fuel pressure in fuel rail. l  With engine idling the figure displayed will be approx. 35 kPa. This is the actual pressure generated by the high-pressure pump in the fuel system.   Note “kPa” is also used as a unit for measuring pressure in addition to “bar”: 1 bar = 1 kPa. 1 -  Control unit identification

–  Pry off cover -1- on left side of dash panel using removal wedge -3409- or similar -arrow-.

–  Pull out fuse number 3 -SC3- (3rd from the top) in brown fuse holder -ST2- in dash panel (driver's side).

Display on -VAS 5051B-: –  With engine still running, check display -2- for fuel pressure in fuel system. l  The fuel pressure will decrease very quickly because the mechanical high-pressure pump is no longer being supplied with fuel from the fuel tank by the electric fuel pump. –  Switch off ignition as soon as fuel pressure has dropped to just below 8 kPa.   Note The fuel pressure must not drop below 6 kPa, otherwise the engine will stall (this could damage the catalytic converter). The fuel rail is still filled with fuel, however it is no longer under high pressure.   WARNING There is a risk of injury: avoid skin contact with fuel. t  Wear safety goggles and protective clothing when opening the fuel system. t  Before opening the high-pressure section of the fuel system, place a clean cloth around the connection to catch escaping fuel. –  Disconnect a fuel line connection without delay.   Note The pressure will increase again due to the effect of residual heat if the high-pressure system is not opened immediately.

Additional steps required –  Insert fuse number 3 -SC3- (3rd from the top) in brown fuse holder -ST2- in dash panel (driver's side). –  Faults are stored in engine control unit because electrical connectors were unplugged and engine was started: “Generate readiness code” in “Guided Functions” → Vehicle diagnosis, testing and information system VAS 5051.