Generic OBD-II scanners aren't recommended because they often will not show a fault code even when a DTC code is stored in one of the modules.
How to read VW fault codes
This is how to read fault codes from all the modules. The same procedure is carried out by the Volkswagen dealership and typically costs $130-$165.
- Get a VW OBD2 All System Scanner.
- Connect the scanner to the OBD-II port under the dashboard. Driver's side.
- Turn on the ignition but do not start the engine.
- Turn on the scanner and select VW from the model list.
- Press OK to read VIN.
- Select a Health Check or Auto-Scan to allow the scanner to read the fault codes from all the modules.
- Review all the modules that have fault codes. Pay attention to ACTIVE codes.
You need to pay close attention to codes that show as ACTIVE or PRESENT. Those codes indicate a current problem that needs to be fixed.
Codes that show as stored or passive can be cleared by going back to the main menu and selecting Clear Fault Codes.
On average, a Volkswagen vehicle, such as Jetta, Golf, Passat, Tiguan, Routan, Eos, etc., will have fifteen modules such as engine control module (ECU), transmission module, ABS module, airbag/srs module, climate control module, window module, etc. Every single module can store fault codes. A fault code is stored in a module that detects that one or more of the sensors that it monitors is operating out of range.
My OBD-II scanner shows no codes, why?
If you are reading check engine light, any OBD-II scanner will work. For example, you can use the UCAN-I scanner which will be able to read and clear check engine codes. If you need to read other fault codes (ABS, Airbag, Transmission, etc) codes, you will need a multi-system Volkswagen OBD-II scanner.
Please don't use a generic OBD-II scanner because they typically only read fault codes from the engine control module (ECM). If you try to read codes related to other modules such as airbag, transmission, ABS, traction control, etc., it will show no code.
To get a full picture of what is wrong with your VW, get a good scanner that can read and clear fault codes from all modules.