VW Advanced Diagnostics & Troubleshooting 3

Question 1

A VW Touareg with air suspension shows fault P0627 – Compressor relay circuit open. Relay tests good. What is the next diagnostic step?

Accepted Answer

Test voltage at the compressor motor feed wire under load

Answer

After confirming the relay is functional, voltage drop testing under load at the compressor motor connector identifies wiring resistance or ground faults that appear only under current draw.

Question 2

During an EVAP system leak test on a VW using the onboard leak detection pump (LDP), the system fails to hold pressure. Smoke testing shows no external leak. What is the most likely cause?

Accepted Answer

Vent solenoid not closing during the test

Answer

If the vent solenoid does not close when commanded, the EVAP system remains vented to atmosphere, causing the LDP to fail to build pressure regardless of canister or cap integrity.

Question 3

A technician scopes the crankshaft position sensor signal on a 1.8 TSI and notices one tooth gap appears wider than the others. What does this indicate?

Accepted Answer

The 60-2 reluctor wheel has a missing reference tooth — this is normal

Answer

The 60-2 trigger wheel intentionally has two consecutive missing teeth as a reference gap to establish TDC, and this wider gap is normal on all VW 60-2 engines.

Question 4

On a VW with electromechanical power steering (EPS), the steering angle sensor requires recalibration after an alignment. Which procedure is correct?

Accepted Answer

Use VCDS Basic Settings to perform steering angle sensor zero-point calibration with wheels straight

Answer

The steering angle sensor zero-point must be set via VCDS Basic Settings with the front wheels in the straight-ahead position to give the ESC and EPS modules an accurate reference.

Question 5

A VW Passat B8 presents with fault P0299 – Turbocharger underboost. Boost pressure measured at 1.4 bar, spec is 2.0 bar. N75 valve is functioning. What should be checked next?

Accepted Answer

Charge air pipe for cracks or disconnected couplings under boost

Answer

After confirming the wastegate solenoid is working, boost leaks from cracked charge air pipes or loose couplings are the most common cause of underboost on the MQB/B8 TSI platform.

(VW) Volkswagen Certified Technicians Practice Test

(VW) Volkswagen Certified Technicians Practice Test

VW Advanced Diagnostics & Troubleshooting 3