Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AUDI

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold on Audi: 8 steps, engines AFB, AKN.

On engines AFB and AKN (platform code 8D), this procedure checks whether the turbocharger reaches charge pressure under load, using measured value display group 011 on diagnostic tester VAS 5051B during a road test. The car is accelerated at full throttle in 3rd gear (or position 2 on automatics) from 2000 rpm, and a second mechanic triggers a printout at about 3000 rpm so the display zone can be read afterwards. If charge pressure is out, the follow-up is a check of the wastegate linkage and vacuum unit, then charge pressure control solenoid valve N75, and only after both pass is the turbocharger itself condemned. The make-or-break part is safety and teamwork: one person drives, the other handles the tester, which must be properly secured.

8 steps 2 engine codes

🧭 Before you start

Connect VAS 5051B, select measured values and display group 011, then road-test with a second mechanic. Accelerate at full throttle in 3rd gear (or position 2) from 2000 rpm and have the helper press PRINT at about 3000 rpm. Read display zone 3 from the printout. If charge pressure is off, check the linkage and vacuum unit, then N75, and renew the turbocharger only if those are correct.

Fits: Audi A4 B5 (8D)

Renewed: turbocharger

Don't miss

The driver must not operate the tester; a second mechanic reads and prints.
Secure the diagnostic tester in the car before the road test.
Use 3rd gear (or position 2) from 2000 rpm and capture at about 3000 rpm for comparable values.
Check linkage, vacuum unit and N75 before condemning the turbocharger.

Written for this job from the workshop steps below · TorqFix editorial.

🔧 Engine codes this applies to

AFB AKN

📐 60 workshop diagrams for AFB

Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 1

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 2

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 3

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 4

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 5

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 6

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 7

Checking turbocharger and charge pressure control - vehicles without plug in intake manifold — AFB · diagram 8

+ 52 more diagrams

🔒 60 workshop diagrams for this job Ask about your Audi AFB — free or sign up free to see the drawings

📋 Procedure

⚠ Accidents can be caused if the driver is distracted by test equipment while road-testing, or if test equipment is not properly secured.Observe safety precautions . — From menu (1), select diagnosis function "“Measured values”" and press → key to continue.
Press keys 11 on keypad (1) to select "“Display group 011”" and confirm entry by pressing Q key.
Accelerate vehicle in 3rd gear (or position 2) from 2000 rpm at full throttle while a second mechanic observes the rev counter.
Second mechanic should press PRINT key on VAS 5051B at approx. 3000 rpm.
Check display in display zone (3).
Check linkage and vacuum unit for charge pressure control .
Check charge pressure control solenoid valve N75.
Renew turbocharger .

Workshop diagrams

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TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.

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Workshop data on this page last updated 20 Sep 2026.