OBDII scanner, unable to communicate with vehicle

FRANKIE11

MEMBER
2005 AUDI A4
1.8L
4 CYL
AUTOMATIC
168,000 MILES

Each time I have tried scanning my vehicle for codes using the OBDII scanner, there is a message on the scanner stating that it is unable to communicate with vehicle. There are lots of issues with my car, but I am not able to correct them because of the OBDII issues. I do not want to continue to buy parts without knowing what the specific issue is. I will appreciate any advice or any help. I checked all fuses and they are all good. However, the fuse for the fuel pump will not light on with the car on or off.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi and thanks for using 2CarPros.com.

Since you are not able to communicate with the vehicle, it could be many things. First, take a look that the partial wiring schematic I attached. It shows the DLC and power and ground for the unit. Check to make sure you have a good ground.

Basically, locate pin 4 or 5 based on which vehicle you have (see schematic for specific model information).

Also, Please reconfirm that both fuses 12 and 31 are good and transferring power.

I noted that you indicate little knowledge. Here are links to help you through this process:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-a-car-fuse-works

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Also, keep in mind VW/Audi always seems different than most. Is the scanner you have capable of communicating with an Audi? I have found that using a scanner designed for VW/Audi (VAG) sometimes is required.

One last question. You mentioned there is no power to the fuel pump fuse. Is the vehicle failing to start?

Let me know if any of this helps or if you have other questions.

Take care,
Joe

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