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Ron, ASE Certified Technician
Category: VW
Satisfied Customers: 35858
Experience:  ASE Certs.
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I was working on my 2012 VW jetta tdi, had to change out the

Customer Question

I was working on my 2012 VW jetta tdi, had to change out the wiper motor. After I installed the new wiper motor I checked all the fuses and relays. I did find a blown fuse. I replaced the fuse. I finished installing the wiper motor. When I started the car all the yellow warning lights, and brake and seat belt, came on (ABS, etc...). The speedometer isn't working either. I can't figure out what the problem is. What would cause all the warning lights to come on and the speedometer not to work.
Submitted: 1 year ago.
Category: VW
Expert:  Ron replied 1 year ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

Any time these warning light come on this usually means the computer is seeing a problem. In order to be able to to try and determine the cause the first thing you need to do is to have the computer system scanned and the codes retrieved. If you can get this scan done and post back with the results, I will try and help you determine the cause. Let me know and we can work from there.

Customer: replied 1 year ago.
I did that already and we got U0121. But all the warning lights are on, not just ABS. I thought it might be because I left the key in the ignition while changing the wipers and that caused the battery to loose voltage. All I would have to is get the codes reset. If that is the case is this the correct code?
Expert:  Ron replied 1 year ago.

What happens if you do a system reboot, try disconnecting both battery cables and touching them together for a few seconds and then reconnect them and see if the problem clears.

Customer: replied 1 year ago.
I did unhook the battery for a few hours but I never touched the ends together. You think touching the ends together will reset it?
Expert:  Ron replied 1 year ago.

Touching them will allow the computer and all the module to reboot. Give it a try.

Customer: replied 1 year ago.
I touched the ends and that didn't help. The battery is reading 12.96 volts.
Customer: replied 1 year ago.
What should the battery read?
Expert:  Ron replied 1 year ago.

Normal battery voltage on a fully charged batter should read right at what you getting, you should be fine at 12.9 volts.

Customer: replied 1 year ago.
When I changed the fuse, it was in relay 645. I did take the top off of the relay. Does this relay control all of those warning lights?
Customer: replied 1 year ago.
i mean I took out 645 to check it and pulled the top off the relay. It looked ok to me. I put the top back on and reinstalled. THat seems to be when all the problems started.
Expert:  Ron replied 1 year ago.

It possiable you may have damaged the relay, do you have another know good one you can replace it with to check it?

Customer: replied 1 year ago.
i tried one that looked like it from autozone they could not find the relay in there did not help. could you tell me if that relay controlls the warning lights and the speedometer.
Customer: replied 1 year ago.
the relay was in the fuse box next to the battery. number 645
Expert:  Ron replied 1 year ago.

I am not seeing any relays that control the instrument cluster. See the wiring diagram in the link below, copy and paste the link to your browser to open and view it.