Volkswagen Workshop Service and Repair Manuals

Both pressure senders are located in the Diesel injection system control unit. Only for vehicles up to 08.94 is the altitude sender-F96 a separate component and is located behind dash panel above the central electrics.

Special tools, testers, measuring instruments and auxiliary items required

• ◆ Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
• ◆ Test box V.A.G 1598/18
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Measuring cable V.A.G 1501
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test sequence

• ‒ Connect fault reader V.A.G 1551 and select engine electronics control unit (address word 01); selection is carried out with ignition switched on.
  

• ‒ Input 08 for "Read measured value block" function and confirm with Q.

• ‒ Press keys 0, 1 and 0 for "Display group number 10" and confirm entry with Q key.

• ‒ Compare display in display zone 2 (altitude sender -F96) and display zone 3 (intake manifold pressure sender -G71).

Specification: Pressures the same
     (Tolerance ±30 mbar)

• ‒ If specification is not attained, compare displayed pressures with a barometer (e.g. Turbocharger tester V.A.G 1397/A), tolerance ±30 mbar:
• ‒ If figure in display zone 3 deviates, pull pressure hose off control unit.
• ‒ If figure in display zone 3 continues to deviate, renew diesel direct injection control unit.
• ‒ If the figure in display zone 2 deviates and 1024 mbar is constantly displayed:

On vehicles from 08.94:

• ‒ Renew Diesel direct injection system control unit.

On vehicles up to 08.94:

• ‒ Check altitude sender as described below.
• Disconnect connector for altitude sender (F96) =>Fitting locations overview, Page 23-4 .
• → Connect cable V.A.G 1501 to sender (F96) and connector.
• Connect vacuum pump V.A.G 1390 to altitude sender (F96) -arrow-.
• Switch on ignition.
• Select measuring range 20 V on hand multimeter V.A.G 1526 and connect to cable test sockets 1 + 2.
       Specification: approx. 5 V
• Connect hand multimeter V.A.G 1526 to cable test sockets 2 + 3.
       Specification: approx. 4.5 V
• Operate vacuum pump,
       Voltage must decrease.
• If the voltage does not decrease, replace altitude sender (F96).

Checking wiring connection to altitude sender (F96)

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

• ‒ Connect test box =>Page23-34 .

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

• ‒ → Wiring from connector contact 1 to test box socket 41.
• ‒ Wiring from connector contact 2 to test box socket 33.
• ‒ Wiring from connector contact 3 to test box socket 40.
• ‒ If neither an open or short circuit exists, renew Diesel direct injection system control unit.