# Fault code U1520



## fredde2011 (Nov 11, 2017)

Have a Chevrolet Cruze LTZ Combi 1.7 diesel -13.
I have an error code: U1520

Does anyone know what it means?

And is it something that could hurt the car?



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## Robby (Mar 1, 2013)

U1520 is a 'Lost communication' code related to the body control module here in the U.S.
It is somewhat generic so my definition may apply to your car.........what country is the car being operated in?

If it was here, my first thought would be to exchange the negative battery cable......a component that was poorly manufactured with a failure rate high enough for G.M. to extend the warranty on.

Have you had any other electrical issues such as the radio going blank, the clock resetting, or all the instrument needles bouncing around?
If anything like that has occured I would exchange the cable before doing any further diagnostics.

Rob


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## fredde2011 (Nov 11, 2017)

The car is in Sweden.

I have had trouble with
The code 54 water in the diesel filter.
even though I have not had any water in the filter or tank.

and I have tried to remove the negative battery pool
to see if the code U1520 disappears but it will return after a while.


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## Robby (Mar 1, 2013)

fredde2011 said:


> The car is in Sweden.
> 
> I have had trouble with
> The code 54 water in the diesel filter.
> ...


If the code is related to the cable the interruption is actually inside the clamp where the cable is crimped. The crimp was inadequate and high resistance develops over time.......so, you cannot see the problem.
Since all these modules are solid state they won't tolerate much voltage variation and codes are the result.

Rob


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## fredde2011 (Nov 11, 2017)

Robby said:


> If the code is related to the cable the interruption is actually inside the clamp where the cable is crimped. The crimp was inadequate and high resistance develops over time.......so, you cannot see the problem.
> Since all these modules are solid state they won't tolerate much voltage variation and codes are the result.
> 
> Rob


Attach a picture on negative battery pole cable.
And it's not just one negative cable but two cables.
even a resistance or whatever it is?









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## Robby (Mar 1, 2013)

Interesting......you folks are getting a entirely different terminal design and I rather like the cables being bolted to the terminal.
This design, however, appears to have three potential ground resistance points.....all easy to service.

So, to get it out of the resistance path, I'd remove and wire brush all of the terminals and eyelets attached to the terminal clamp as well as the clamp to post interface and, if you can get to a few of the terminals at the other end of the cable, clean those as well.

Since the negative is off, freshen up the positive as well.

Beyond these suggestions, if not successful, you may have a internal problem with the bcm itself......something along the lines of a cold solder joint that would require replacement of the unit. 
Since your car is not U.S. spec. I don't know the component location but once you find it, remove the multi wire connector and see if there is any corrosion visible (white powdery looking) on the male/female pins. Sometimes, the act of removing and reinstalling the connector will clean the connections and you can carry on.

Regards,
Rob


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## CruzeDan (May 17, 2015)

U codes are not generally something you should be concerned about, they come and go. If you have a code stored current then that is something to worry about.


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## fredde2011 (Nov 11, 2017)

Here's a description of what happens to the car and when the code U1520 comes up.

We can start by removing the negative pole on the battery, then the car resets.

puts back the cable and turns on the ignition no code. starts the car and stops it.

If the car starts again after a while, turns on ignition, the car does its system control, then the code will come up.

But I would turn the key directly to start without ignition, so the code will not come up.

So what could it be?

low volt on the battery?

ignition?

fuel pump?

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## fredde2011 (Nov 11, 2017)

Now hope that the error code is fixed.

It was a power sound module for the alarm system that was broken.

Thank you all who have come with tips and advice.
















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