# Just received a U3501 code



## Tigloo (Oct 27, 2021)

Just got a check engine warning light today and when I scanned it, it came up as a U3501 code which I would guess can be caused by a number of things. I'm planning on setting an appointment with the dealership to have this looked at but wondering if anyone would know if my hardwired (always on) dash cam could've caused this? Low voltage + freezing cold temperature? I've noticed that my dash cam would be off despite it being hardwired after not having driven the car for a day or so.

I'm attaching a screenshot of the fault code. Thanks!


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## OhioSpyderman (Jul 21, 2021)

Care to share how/where you did the hardwire?









Fuse Box Diagram Volkswagen Tiguan 2, 2016 - 2021







car-box.info





Bob.


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## OhioSpyderman (Jul 21, 2021)

I maybe should have said that I am not looking to do a hardwire for a detector (or anything else), just trying to help you figure out why what happened, happened.

Bob.


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## Tigloo (Oct 27, 2021)

OhioSpyderman said:


> Care to share how/where you did the hardwire?
> 
> 
> 
> ...


Based on the diagram, I hardwired these to F35 and F19.


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## Tigloo (Oct 27, 2021)

OhioSpyderman said:


> I maybe should have said that I am not looking to do a hardwire for a detector (or anything else), just trying to help you figure out why what happened, happened.
> 
> Bob.


Yeah, that was a bad idea and I already unplugged the dash cam and will probably just plug it in the 12v charger in the cabin. Still waiting on a confirmation from the dealership but I'll try and clear the code and see if disconnecting the hardwire changes anything. Will probably have to run the car a bit to charge the battery if ever that was the issue.


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## OhioSpyderman (Jul 21, 2021)

Two power inputs and a ground?
Assuming one is constant and one is key switched?

Bob.


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## OhioSpyderman (Jul 21, 2021)

I would have probably picked F40 (it's for the 12v socket).....just saying...

Bob.


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## Tigloo (Oct 27, 2021)

OhioSpyderman said:


> I would have probably picked F40 (it's for the 12v socket).....just saying...
> 
> Bob.


Yep, one constant and one key-switched. F40 for just the key-switched right? Probably smart to not just plug in the constant since it might actually drain the battery. I'll test that out and see how it goes. Thanks!


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## OhioSpyderman (Jul 21, 2021)

I'm honestly not sure what is key switched and what is constant, I'm a VW newbie, lol.
Assuming the constant is to keep the time and date info in the cam from getting messed up?

I would really like to know what the "reserved" (empty) sockets are/are for/are capable of ?????

Bob.


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## Tigloo (Oct 27, 2021)

OhioSpyderman said:


> I'm honestly not sure what is key switched and what is constant, I'm a VW newbie, lol.
> Assuming the constant is to keep the time and date info in the cam from getting messed up?
> 
> I would really like to know what the "reserved" (empty) sockets are/are for/are capable of ?????
> ...


The constant is to keep the dash cam running even when the ignition is off. 

My best guess is that the empty fuses/sockets are for extra accessories when needed (?).


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## OhioSpyderman (Jul 21, 2021)

Your last question/statement would make me call the dealer and find out.
THEY might be the best choice for your "hardwired dash cam".....

I'm not an Electrical Engineer, but I did stay at a Holiday Inn last night.....
(Seriously, I am a retired Software Engineer, with just enough knowledge of electric/electronics, to get me in trouble...lol)

Bob.

EDIT: I see "old" humor is not appreciated here...


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## jonese (Jun 21, 2020)

I do/did the same thing (one switched feed, one constant) to my dashcam. After a week, I had an error (different than yours mind you, it was I think quiescent current message). In the end, I didn't like the additional 10-20ma draw on my battery and got rid of the parking dashcam feature. I only use switched power (T15) now.

I'm using fuse position 34 with a piggy back 3 amp fuse (many dashcam kits provide you with silly 10/20 amp fuse).

edit:
Here was my error (U1406) on the Gateway module 19:

8531970 - Quiescent Current
U1406 00 [008] - Too High
[Ruhestrom oberer Grenzwert überschritten]
Intermittent - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 7
Fault Frequency: 1
Reset counter: 50
Mileage: 19852 km
Date: 2021.09.14
Time: 00:40:21

Terminal 30 power supply: 12.2 V
Terminal 15: OFF


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## OhioSpyderman (Jul 21, 2021)

This position 34?


347.5A Rotary light switch EX1
Interior rearview mirror EX5
Socket relay J807
Switch for reversing lights F4
Pressure sensor in the air conditioning circuit G805
Air pollution sensor G238
Button for electromechanical parking brake E538
Button for disabling ASR and electronic stability control E256

If so, I'm not sure why you guys (gals...to be politically correct) aren't picking circuits with "less" circuitry?

Again, I ask, what are the "reserve" sockets for/capable of?

Bob.


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## jonese (Jun 21, 2020)

Yea, that's the one, I remember clearing a parking brake error after my install.

In my case, I was only effectively adding 800-1000 ma worst case during dashcam start up. The other rational for that specific position was physical layout and placing the piggy back circuit (just as OP has) where the new circuit lead would route cleanly.

I believe someone else had added a new fuse position and pinned it out properly, making it look very clean. But, that leaves evidence, and if VW wanted to deny warranty on an electical item, they could use that (it's been said splicing into electrical wiring will void the warranty on electronics).


Back to the OP's question. I'm not sure if your error is related, but it looks like it.

There was a comment on the VCDS forum about this error and the solution was to simply charge the battery.


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## OEMplusCC (Jan 27, 2013)

Regards to code U3501. My wife gets it here and there. I never found a definitive root cause but I am fairly certain it has something to do with "low battery and car's remote start procedure".
Let me explain.
This issue only sporadically occurs under two conditions. Car has been sitting for 2+ days AND its started via remote.
As soon as the check engine light comes on the engine shuts off (normal for remote start, safety thing).
The battery is original which means it was made sometimes in 2018. I am assuming that its simply the first sign of battery slowly getting old.
However, there is a catch.... I also have a small aftermarket amplifier which auto turns on with the radio. So in my case this could be exaggerating this condition as well.

My conclusion is simply, there is a point in time of the car startup sequence where the battery level must be 11V or more(or some voltage). If that voltage is not reached it will throw this error. Now why that voltage is not reached could be due to many reason. Older battery, aftermarket amp, aftermarket radar or simply some other draw.
In my case, the sequence is like this
_car has been sitting for 2+ days(original battery) -> remote start -> ignition on -> radio on -> amp on -> extra current draw on battery -> bellow 11V? at certain critical point in time -> boom U3501 check engine light _

I mention this to my dealer but they said I would have to remove my amplifier for them to troubleshoot it under warranty(and conclude its not my small amp). I think that is fair request... I decided to leave it as is. This rarely happens, usually when we dont drive the car(holidays etc) + remote start. Happened total 3 times in 2 years. I just simply clear the code and go about my day.

Here is address 01 Engine VCDS scan for info (and future googlers)


```
1 Fault Found:
40571 - Voltage Supply 1 for Control Module
          U3501 00 [232] - Too Low
          MIL ON - Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 6
                    Mileage: 27846 km
                    Date: 2021.11.11
                    Time: 10:28:09

                    Engine RPM: 1117.50 /min
                    Normed load value: 39.2 %
                    Vehicle speed: 2 km/h
                    Coolant temperature: 24 °C
                    Intake air temperature: 23 °C
                    Ambient air pressure: 980 mbar
                    Voltage terminal 30: 10.800 V
                    Unlearning counter according OBD: 40
                    Engine status: COENG_RUNNING
                    Engine status-Test_Program_Co Eng st COMPU VERB UBYTE: 3
```

but please post back with your result from the dealer. I am super curious if your dealer will actually try to troubleshoot it further. Everything above is just my observation, it might be right it might be completely wrong or something in between


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## sp_golf (Nov 28, 2007)

Here's a scenario of what's going on:

Your dash cam drains the battery, then your starter drains it, then the engine and accessories are running off of it.
Your alternator doesn't start charging right away so you get a low voltage code.


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## VW ENGINEERING (Jan 7, 2022)

Can you pull your 12V battery idle voltage with obdeleven or Ross-Tech.com? this information alone will help me tell you what is your problem?


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## VW ENGINEERING (Jan 7, 2022)

Post #15 have 12V battery inspect out of the car for SOH ....10.80 V will cause all types of problems on can bus and modules.


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## VW ENGINEERING (Jan 7, 2022)

To find out your ghost users you can use clamp current meter....post your car off idle stats and i will chime in.


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## OEMplusCC (Jan 27, 2013)

VW ENGINEERING said:


> Post #15 have 12V battery inspect out of the car for SOH ....10.80 V will cause all types of problems on can bus and modules.


Yep. Its pretty clear to me that type of low voltage can cause problems. Thats why i never bothered going through warranty. It was pretty clear its the battery or the extra draw from the amp. Ill just live it it.

Thanks for the response

Sent from my Pixel 4a using Tapatalk


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## mattchatr (Jan 26, 2018)

I have been getting this same U350100 code for last several months, been getting it like others have said, when I've used the remote start....doesn't matter if its winter or summer but I do think its due to a low battery. I trickle charged my battery last night so going to see how that holds up (the meter did say it was low, so its likely time to get a new battery). I do have some aftermarket lighting setup so that might be partially the culprit as I'm likely putting a bit of extra strain on the car (like the fellow with the amp as well). I'll report back if I find anything else, otherwise its a quick code clearing when it does happen.


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## Flogrown2000 (5 mo ago)

mattchatr said:


> I have been getting this same U350100 code for last several months, been getting it like others have said, when I've used the remote start....doesn't matter if its winter or summer but I do think its due to a low battery. I trickle charged my battery last night so going to see how that holds up (the meter did say it was low, so its likely time to get a new battery). I do have some aftermarket lighting setup so that might be partially the culprit as I'm likely putting a bit of extra strain on the car (like the fellow with the amp as well). I'll report back if I find anything else, otherwise its a quick code clearing when it does happen.


I have a stock setup and got it enough to lower my engine power, Power steering, and give me an engine check light.


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## 08CandyWhite (Jan 31, 2003)

I had U350100 as a soft fault in my Tiguan's system for a while about a year ago. I had it throw a hard fault and CEL for the same code twice. I found this to be caused by a fatiguing main battery. Not able to hold a high enough charge constantly to keep all the systems happy. 

I replaced and coded the replacement battery (000-915-105-CC-DSP) from VW. Made sure to change it's coding to know it was an AGM battery I installed in the Tiguan. Fault has not returned since.


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## Salle071 (Jun 5, 2007)

I get U3501 here in Canada in the winter once a week if I am not driving every day. 2020 Tiguan. It is around -15 and -35C outside. I just ignore it and it goes away on the next start. Neve in the summer.


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## OEMplusCC (Jan 27, 2013)

I can confirm this is mostly due to low battery voltage. I have replaced battery recently and this issue has not reoccured. To me this error is just "the thing" this car does when battery gets low


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## saqunita (17 d ago)

Tigloo said:


> Just got a check engine warning light today and when I scanned it, it came up as a U3501 code which I would guess can be caused by a number of things. I'm planning on setting an appointment with the dealership to have this looked at but wondering if anyone would know if my hardwired (always on) dash cam could've caused this? Low voltage + freezing cold temperature? I've noticed that my dash cam would be off despite it being hardwired after not having driven the car for a day or so.
> 
> I'm attaching a screenshot of the fault code. Thanks!
> 
> View attachment 146392


so what does this code mean is it something that would be covered by manufacture or warranty


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## jonese (Jun 21, 2020)

I suggest it wouldn't be a warranty item if the cause was parking mode on the dash cam (meaning constant excessive current draw).


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