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AudiDoc, Independent Audi Shop Owner
Category: Audi
Satisfied Customers: 1695
Experience:  I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
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I have a 2004 Audi a4 cabrio Quattro with 3.0L engine. I

Customer Question

Hi, I have a 2004 Audi a4 cabrio Quattro with 3.0L engine. I have been chasing some faults in the electrical system now for a few months. When I run a scan with vagcom or obdeleven pro I get numerous codes on several modules. The one that is most prevalent is modules ,01 engine, 03brakes, 09 central electric. I get data bus no communication on all. I can't code the abs brakes because of no communication. I had to replace ABS pump and module. #'s are the same. I also get power supply terminal 30: voltage too low. battery connections are good and has not been disconnected. Here is the latest scan 01-- p1649, databus drivetrain missing message from abs control module (static). 03--p1623(18031) Databus drivetrain no communication (static; p1826(01826) Voltage supply terminal 30 too low (static); p1854(18262) Databus drivetrain faulty (static); p1850 Databus drivetrain missing msg. from engine control module; p01044 control module incorrectly coded. Coding login is 09397 and coding is 04497. 09--01312 Drivetrain data bus (static).
I'm at a loss. I hope it's something simple as battery not putting out enough or alternator going bad. Battery connections are good and has not been disconnected. I'd appreciate your thoughts ***** *****
Submitted: 3 months ago.
Category: Audi
Expert:  david craig replied 3 months ago.

Hi Im David. whats the battery voltage while the vehicle is running?

Customer: replied 3 months ago.
14.11 volts
Expert:  david craig replied 3 months ago.

not perfect, a little low it should be around 14.4. whats the battery voltage without it running?

Customer: replied 3 months ago.
12.36 volts. The car had this trouble when I bought it. I got it for a song and I'm just trying to fix it.
Expert:  david craig replied 3 months ago.

12.36 is a bit low also. it should be 12.50. clean up the battery terminals and starter cable.

Customer: replied 3 months ago.
Would it be that sensitive to not respond on .14 of a volt?
Expert:  david craig replied 3 months ago.

yes

Customer: replied 3 months ago.
Then since the battery is fairly new, I'm going to look toward the alternator. I'll clean all connections. I have added ground straps from battery to the frame and frame to the engine. I'll get back to you later Sam
Expert:  david craig replied 3 months ago.

sounds good

Customer: replied 3 months ago.
David, Voltage readouts from vagcom with engine running. Idle- 13.9 to 14.1, 3000 rpm -14.1. back to idle- 14.0. Voltage when car isn't running is 12.35
Customer: replied 3 months ago.
I cleaned and tightened all connections
Customer: replied 3 months ago.
Is my alternator weak and could be causing a lot of the voltage and communication issues? thanks, Sam
Expert:  david craig replied 3 months ago.

i absolutely believe that Sam. it may not seem like alot, but it matters. its messed many techs up before.

Expert:  david craig replied 3 months ago.

any update?

Customer: replied 3 months ago.
I had to order a new alternator. Be a couple days
Expert:  david craig replied 3 months ago.

ok

Expert:  david craig replied 3 months ago.

any news?????????

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