Testing charge pressure control function via load signal — AUDI

AZB
Notes:

A second operator is required to note readings with the vehicle moving.
Observe safety precautions => Page
21-9
.
The vehicle tester system V.A.G 1552 can also be used instead of fault reader V.A.G 1551.

Unclip cover for diagnostic connection.
Connect fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3.

V.A.G - SELF DIAGNOSIS
HELP
1 - Rapid data transfer 1)
2 - Flash code output 1)
Indicated in display

1)
appears alternately

Note:

If the display remains blank:

=> Fault reader operating instructions

Press key 1 for "Rapid data transfer".
Start engine.

Rapid data transfer
HELP
Enter address word XX
Indicated on display:

Rapid data transfer
Q
01 - Engine electronics
Press keys 0 and 1 for address word "Engine electronics" and confirm entry by pressing the Q key.

06A906018..
1.8l
R4/5T MOTR HS
0...
" Coding 04000
WSC 12345
The display on fault reader V.A.G 1551 will show the control unit identification.

Press ⇒key.

Rapid data transfer
HELP
Select function XXX
Indicated on display:

Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Read measured value block
HELP
Enter display group number XXX
Indicated on display

Enter display group number 025 and confirm entry with Q key.

Read measured value block
25
⇒
1
2
3
4
The measured value block shows 4 display zones: => Page
21-35
for explanation of readings in display zones 1 ... 4.

Explanation of readings in display zones

Read measured value block
25
⇒
1
2
3
4
Indicated in display

Display zone · Reading
1 · Disregard reading
2 · Specified engine load (after correction)
3 · Actual engine load
4 · Duty cycle (activation of solenoid valve for charge pressure control -N75)

Watch readings in display zones 2 and 3 while vehicle is accelerated at a constant rate.
Specification:
Difference between readings 2 and 3 must not be more than 0.3 ms.

Note:

If faults in the charge 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 %.

Faults in charge pressure control function

Fault · Display on V.A.G 1397 A · Display on V.A.G 1551 · Possible causes of fault
Charge pressure too low · ▪ Reading below 1.370 bar / ▪ (vehicles with manual gearbox) / ▪ Reading below 1.300 bar / ▪ (vehicles with automatic gearbox) · ▪ Actual engine load (display zone 3) less than specified engine load (display zone 2) / ▪ Duty cycle (display zone 4) tends towards 99% · - Solenoid valve for charge pressure control -N75 defective / - Wiring to solenoid valve for charge pressure control defective / - Charge pressure regulating valve in turbocharger jammed in open position / - Leaks between turbocharger and intake manifold / - Turbocharger defective
Charge pressure too high 1) · ▪ Reading above 1.470 bar / ▪ (vehicles with manual gearbox) / ▪ Reading above 1.400 bar / ▪ (vehicles with automatic gearbox) · ▪ Actual engine load (display zone 3) higher than specified engine load (display zone 2) / ▪ Duty cycle (display zone 4) tends towards 0% · - Pressure unit for charge pressure regulating valve defective / - Hoses to pressure unit for charge pressure regulating valve (via -N75) leaking / - Charge pressure regulating valve in turbocharger jammed in closed position

1)
If the charge pressure is too high the fuel supply will be interrupted in order to protect the engine. This results in misfiring at high engine speeds.