Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
CAN-bus, checking (from MY 2000): Notes
Function
The Engine Control Module (ECM) communicates with all control modules capable of data bus via CAN data bus.
The control modules capable of data bus are connected together via two data bus wires twisted together (CAN high and CAN low) and exchange information (messages). Missing information on the data-bus is recognized as a malfunction by the Engine Control Module (ECM) as well as by other CAN-bus control modules.
Further information WSP 521 419 00The CAN data bus.
The data bus requires a matching resistor to function fault free. This central matching resistor is located in the engine control module.
- Read which control modules are actively connected via data bus to the engine control module in measured value blocks 125 and 126.
Special tools, testers and auxiliary items required
- Test box V.A.G 1598/31
- Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
- Adapter set V.A.G 1594
- Wiring diagram
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.