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 (through MY 1999): Function
The Engine Control Module (ECM) ( ) communicates with the ABS Control Module ( ) and the Transmission Control Module (TCM) ( ) via a CAN-Bus ( ).
At least two Control Modules capable of CAN-Bus are connected together via two CAN-Bus wires which are twisted together (CAN_High and CAN_Low) and they exchange information (messages). Missing information on the CAN-Bus will be recognized as a DTC by the Engine Control Module (ECM) as well as by other CAN-Bus Control Modules.
Two Control Modules have terminal resistors each of 120 Ω, these resistors make sure that the CAN-Bus can function without a malfunction. These terminal resistors are located in the engine and ABS Control Modules.
Special tools, testers and auxiliary items required
- Test box V.A.G 1598/22 (through my 1999)
- Test box V.A.G 1598/31 (from my 2000)
- Digital multimeter US 1119 (Fluke 83 or equivalent)
- Adapter set V.A.G 1594
- Wiring diagram
Vehicles with manual transmission
- Test box V.A.G 1598/21
Vehicles with automatic transmission
- Test box V.A.G 1598/18
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.