Testing boost pressure - engine code AFN, AHH: Audi 1.9 TDI (1Z, AFF, AFN, AHH, …)

AFF AFN AHH AHU AVG
A modified injection system is fitted on vehicles 07.97 ä, on which the connection hose to engine control unit is discontinued. The turbocharger tester cannot be connected to this injection system. The boost pressure can only be checked using fault reader V.A.G 1551.
This section describes the test using both measuring devices.

Special tools, testers and auxiliary equipment required

V.A.G 1397 A (only for vehicles ä 06.97)

VAS 5051

or

V.A.G 1551 with V.A.G 1551/3 A

Test sequence

On vehicles ä 06.97, disconnect connecting hose between rear air duct pipe and engine control unit and connect to T-piece of turbocharger tester V.A.G 1397 A.
Route measuring hose under rear edge of bonnet and into passenger compartment via right hand window.

Switch on turbocharger tester and set measuring range selector switch to position -I- (absolute pressure).
Connect measuring hose to connection -I-.

Notes:

Hose connections must be completely airtight, otherwise measurements will not be correct.
Ensure that measuring hose is not pinched at bonnet or side window.
Pressing memory key M on turbocharger tester will store the last measured value until memory key M is pressed again or tester is switched off.
The decimal point in the display flashes to indicate that the value is being stored.
If the battery voltage of the turbocharger tester drops below the minimum level, an arrow will appear at the top left of the display.
Observe safety precautions => Page
21-8
.

Read measured value block, display group 011:

=> Diesel direct-injection and glow lamp system (4-cyl.) ä 06.97; Repair group 01; Self diagnosis of diesel direct-injection system; Reading measured value block
Diesel direct-injection and glow lamp system (4-cyl.) ä 06.97
Self diagnosis of diesel direct-injection system
Reading measured value block

=> Diesel direction-injection and glow lamp system (4-cyl.) 07.97 ä; Repair group 01; Reading measured value block
Diesel direction-injection and glow lamp system (4-cyl.) 07.97 ä
Reading measured value block

Read measured value block 11
⇒
840 rpm
938 mbar
978 mbar
92 %
Display:

Measure the boost pressure at full throttle.
Accelerate from 2000 rpm at full throttle in third gear (or with selector lever at position 2), and watch rev counter.
Press PRINT key on V.A.G 1551 and memory key M on V.A.G 1397 A simultaneously at approx. 3000 rpm.

Specified values:

Specified value on V.A.G 1397 A:
1.850 ... 2.200 bar

Read measured value block 11
⇒
3000/min
2190 mbar
2190 mbar
42 %
Specified value on V.A.G 1551:
1850... 2200 mbar (in display zone 3)

Notes:

On vehicles ▸ 06.97, boost pressure level is measured with turbocharger tester V.A.G 1397/A. Fault reader V.A.G 1551 is then used to check whether boost pressure is being registered by the control unit.
On vehicles 07.97 ▸ boost pressure can only be checked using V.A.G 1551.

If the boost pressure is not obtained:

Leak between turbocharger and intake pipe
Fault on linkage or vacuum unit for boost pressure control. Checking => Page
21-25
Turbocharger defective (turbine sticking because of foreign body)