VW Electrical Systems & Wiring 2

Question 1

In a VW CAN bus network, what does a 'bus off' state indicate?

Accepted Answer

A node has detected too many errors and removed itself from the bus

Answer

A 'bus off' state means a CAN node has exceeded its error count threshold (255 transmit errors) and has disconnected itself from the bus to prevent corrupting communications.

Question 2

Which tool is required to properly terminate a VW Micro-Timer connector during a wiring repair?

Accepted Answer

VW special tool VAS 1978A or equivalent micro-crimper

Answer

VW Micro-Timer connectors require the VAS 1978A micro-crimper (or OEM-equivalent) to achieve the correct crimp geometry; improper tools cause intermittent contact failures.

Question 3

When diagnosing a no-start caused by a faulty immobilizer, which component stores the transponder adaptation data in most MQB-platform VW vehicles?

Accepted Answer

Instrument Cluster

Answer

On MQB-platform vehicles, the instrument cluster stores the immobilizer adaptation data and acts as the security gateway between the transponder and the ECM.

Question 4

A technician measures 0.4 V on a B+ feed wire under load where 12 V is expected. What does this most likely indicate?

Accepted Answer

High resistance in the circuit, such as a corroded connector or fusible link

Answer

A severe voltage drop (nearly all voltage consumed before reaching the load) indicates high resistance—typically a corroded connector, damaged fusible link, or poor splice—not a short.

Question 5

What is the function of the terminal 15 relay (KL15) in VW electrical architecture?

Accepted Answer

It switches battery voltage to ignition-dependent accessories when the ignition is on

Answer

The KL15 relay distributes switched ignition voltage (terminal 15) to systems that should only be powered with the ignition on, such as the ECM and HVAC.

(VW) Volkswagen Certified Technicians Practice Test

(VW) Volkswagen Certified Technicians Practice Test

VW Electrical Systems & Wiring 2