Check exhaust turbocharger and charge pressure control valve - Engine codes AEB, AJL — AUDI

AJL ANB APU
Special tools and workshop equipment required

Turbocharger tester V.A.G 1397 A

Test requirements:

All hoses and pipes must be checked for tight seating and leakages.
Fault memory has been interrogated

=> Motronic injection and ignition system (4 cylinder Turbo); Repair group 01
Motronic injection and ignition system (4 cylinder Turbo)

Final control diagnosis has been performed

=> Motronic injection and ignition system (4 cylinder Turbo); Repair group 01
Motronic injection and ignition system (4 cylinder Turbo)

Test sequence

Important:
Always attach testers and measuring instruments to the back seat and have a second person operate them from there.
If test equipment were operated from the front passenger seat, the person sitting there could be injured if the front passenger airbag were triggered in the event of an accident.

Connect T-piece with measuring hose of turbocharger test unit V.A.G 1397 A onto front of intake pipe.
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.
Before checking drive vehicles for at least 3 km speedily (without having to stop at traffic lights or similar).
A second operator is required to note readings with the vehicle moving.

Vehicles with engine code AEB:

Accelerate the vehicle from 2000 rpm at full throttle in third gear, and watch the rev counter.
Press recall button -M- at turbocharger test unit with 3000 rpm.
Specified value: 1.370 ... 1.470 bar

If specified value not attained =>Fault table, Page
21-15

Vehicles with engine code AJL:

Accelerate the vehicle from 2000 rpm at full throttle in third gear, and watch the rev counter.
Press recall button -M- at turbocharger test unit with 2500 rpm.
Specified value: 1.800 ... 1.900 bar

If specified value not attained =>Fault table, Page
21-15

Check charge pressure control via load signal - Engine codes AEB, AJL

Note:

On vehicles with automatic gearbox it is not always possible to test the boost pressure control function reliably by checking the boost pressure. Therefore the checking of the boost pressure control via load signal must be carried out with pressure values on lower tolerance limit.

Test requirements:

Connecting vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551.

Test sequence

Read measured value block
25
⇒
1
2
3
4
Read measured value block Display group 025, Engine idling.

Watch readings in display zones 2 and 3 while vehicle is accelerated at a constant rate.
Specified value:
Deviation between display 2 and 3:
max. 0.3 ms

Note:

If faults in the boost pressure control function are detected by the self diagnosis of the control unit, the duty cycle (display zone 4) will be set to a constant 5 %.

If specified value not attained =>Fault table, Page
21-15

Fault in boost pressure control

Fault · Possible causes of fault
Boost pressure below specified value · - The boost pressure control solenoid valve -N75 defective =>checking, Page 21-52
Boost pressure above specified value 1) · - Vacuum unit for boost pressure control valve defective =>Replacing exhaust turbocharger, Page 21-52

1)
When boost pressure is too high the fuel supply is switched off to protect the engine. This results in misfiring at high engine speeds.