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David, VW Master Technician
Category: VW
Satisfied Customers: 2366
Experience:  VW Master Technician Certified for 9 years, ASE Master Technician Certified
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Volkswagen Jetta: 2001 vw Jetta 1.8t Just changed the coil

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2001 vw Jetta 1.8t
Just changed the coil on plug and plugs
Car cranks but won't start
Vagcom Error code
ECU - No Communications
Checked ECU 15amp fuse - it is ok
What to do now?
Did you check all of the fuses? This is a common issue, as the fuse for the coils is also the power supply to the ECM. Check all of the fuses at the fuse box next to the dash. Let me know what you find for further.
Customer: replied 4 years ago.

I checked all the 15 amp fuses and several others. All were fine. Could you be more specific regarding which fuses I should be checking.

Let me look at the diagram, give me a minute. Be right back
Customer: replied 4 years ago.


Customer: replied 4 years ago.

any luck?

I am having a problem getting into the system to download a diagram, but I do have the fuse box diagram. Also check the fuses at the Power supply relay, see both links below.

Fuse diagram

Power supply relay

Check fuses 10, 12, 28, 29 and 32, along with the fuses at the power supply relay
David and other VW Specialists are ready to help you
Customer: replied 4 years ago.

Ok, I checked 28, 29 and 32 but not the others and not the power supply relay. I will check them tomorrow. If they turn out to be ok, what how do I contact you for further troubleshooting?

The next step would be to check the power supply relay. This relay provides power to the ECM. I think you will find a fuse at the relay box. let me know what you find in the morning. I will also try to get a diagram again
Customer: replied 4 years ago.

Ok fuse in slot 10 was blown and every time i replace it and turn on the ignition it blows again. Obviously a short somewhere, but the question is where. Also, there are no other fuses in the power supply relay box other than the 428 and 100 relays themselves. Auto store did not have these in stock so no chance to swap them. All other fuses were ok (12, 28,29, 32)

Unplug all four coils and then see if the fuse continues to blow. Also check closely the wiring to the fuses, have seen several of these harness crack the wiring cover and cause a short.
Customer: replied 4 years ago.

Thanks David. Unfortunately I'm running out of time as the car is in a friends' garage overstaying its' welcome. I should have thought of pulling those damn coils off after blowing the 3rd fuse. I really want my 70 GTO back because it was a hell of a lot easier to play with. When I put the new coils on I did notice a nick on a black wire going into the connector on the cylinder that was misfiring. I checked all 4 wires for issues and only spotted the nick which I taped. I'm assuming when I pull the coils off the fuse will not blow - we'll see.


BTW, I called the local VW dealers today, described the problem, asked for a price to install a wire harness but they told me I had no clue. Funny.

There is also one other item to check if the fuse continues to blow. I ran into this once, and what we found was that the dome light was also wired to the same fuse. One year only, and I believe it is the 2001 Turbo Jetta. If the tab or switch is loose it can cause the fuse to blow. If the slider is loose or you are not sure, remove the dome light and unplug it.