Volkswagen Workshop Service and Repair Manuals

The exhaust gas recirculation and air mass meter function can be checked with the help of final control element test and at the same time calling-up measured value block 03. To do this it is required to activate the control element Exhaust gas recirculation (EGR) valve -N18 and then exiting the final control element test with -C- key. Using this sequence the EGR valve continues to be pulsed so that with the help of measured value block 03 (display zone 3) the extreme values for the EGR (air mass meter) can be read.

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
• ◆ 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 engine idling.
  

• ‒ Input 03 for "Final control diagnosis" function.

• ‒ Confirm entry with Q key.

• ‒ Press ⇒key.

Note:

Control of the individual control elements is limited to 30 seconds. The following switching sequence must therefore take place rapidly so that sufficient time to read off the specifications exists.

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

• ‒ Press keys 0, 0 and 3 for "Display group number 3" and confirm entry with Q key.

• The displays in display zones 3 and 4 must fluctuate within following control range:

Engine code 1Z, AHU:

• ‒ Specification display zone 3
       Lower range 230...310 mg/stroke
       Upper range 360...480 mg/stroke
• ‒ Specification display zone 4
       Lower range 2...5%
       Upper range 90...95%

Engine code AFN:

• ‒ Specification display zone 3
       Lower range 180...320 mg/stroke
       Upper range 370...550 mg/stroke
• ‒ Specification display zone 4
       Lower range 2...5%
       Upper range 90...95%

Because the fault reader display is slow the displayed figures vary greatly. Therefore only ensure that the upper and lower range figures in display zones 3 and 4 are obtained. This means only regard the minimum or maximum values.

• ‒ If specifications are not attained, check air mass meter and exhaust gas recirculation valve as follows:

Checking voltage supply from air mass meter (G70)

• ‒ Disconnect connector for air mass meter =>Fitting locations overview, Page 23-4 .

• ‒ Switch ignition on.
• ‒ Select 20 V measurement range.
• ‒ → Carry out voltage measurement with hand multimeter V.A.G 1526 between the following connector contacts:

If the specification is not attained:

• ‒ Check wiring connection to (G70).

Checking wiring connection to air mass meter (G70).

• ‒ Switch off ignition.

• ‒ Connect test box .

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 19.
• ‒ Wiring from connector contact 2 to test box socket 33.
• ‒ Wiring from connector contact 3 to test box socket 23.
• ‒ Wiring from connector contact 5 to test box socket 1.
• ‒ Wiring from connector contact 6 to test box socket 13.
• ‒ Rectify any open/short circuit as necessary.
• ‒ If neither an open or short circuit exists, renew Diesel direct injection system control unit.
• ‒ If the specifications are achieved and the wiring connections are OK. then replace air mass meter.

Electrically checking exhaust gas recirculation valve (N18)

• ‒ Pull connector off valve =>Fitting locations overview, Page 23-4 .
• ‒ → Measure resistance of valve -N18.
       Specification: 14 ... 18 ω

If the specification is not attained:

• ‒ Replace valve.

Note:

At room temperature the resistance is in the area of the lower tolerance and when engine is at operating temperature in region of upper tolerance.

Checking voltage supply for exhaust gas recirculation valve (N18)

• ‒ Pull connector off valve =>Fitting locations overview, Page 23-4 .
• ‒ → Connect hand multimeter V.A.G 1526 with aux. cables from V.A.G 1594 to connector contact 1 and engine earth.
• ‒ Switch ignition on.
• ‒ Specification:
       approx. battery voltage

If the specification is not attained:

• ‒ Check wiring connection to valve -N18.

Checking wiring connection to exhaust gas recirculation valve (N18)

• ‒ Switch off ignition.
• ‒ Connect test box .

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 68.
• ‒ Wiring from connector contact 2 to test box socket 25.
• ‒ Rectify any open/short circuit as necessary.
• ‒ If neither an open or short circuit exists, renew Diesel direct injection system control unit.