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OBC Onboard Charger issue

657 Views 38 Replies 4 Participants Last post by  ekvals
Hi all, new member here.

Woke up the other morning and discovered that the fuse for the garage had switched off during the night. The 500e was being charged via the outlet charger.
After switching the fuse back on, there was a notification on the instrument panel saying "service charger system", and something along the line "plug not being detected". At the same time the flagpost where flashing.
After trying another charger (charging box), disconnecting 12v and HV, there seem to be no way the car would like to accept charging. Note that car is fully drivable, but obviously it will run out juice in not too long if used.

When charger is connected, and this attempts to charge the car, there is a sound coming from the OBC as you can hear in this video clip.
OBC Video

Question is if this is sufficient to conclude that I have a OBC issue?
Does anyone know if a used unit is a "simple" replace procedure, or does it need to be coded to the car in any way?

Any tip you may have will be greatly appreciated!
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If the pro's reader is Bluetooth, it shouldn't do any harm, but it might not work, as you know first-hand by trying other Bluetooth readers that aren't Veepeak or Konnwei (tested by this forum's members) or listed about halfway down the home page of (tested by them).

You never know when you're going to get the contactor glitch that prevents starting and charging, so if you plan to keep the car you should have a working OBD reader in the car at all times to fix it. It should be one that works with AlfaOBD* on a device which you can keep charged up in the car, whether that's your own phone or laptop, or a cheap Amazon phone kept charged in the glovebox USB.

* MultiECUScan doesn't appear to have the contactor enable function.
Since you skipped the part about OBD so far, it would be nice if you could confirm doing everything else on the lists, because often the false alarm codes won't clear until after doing the first two steps here:
  • Left sensor unplugged, at least until all issues are resolved
  • Disconnected 12V & HV 30+ hours
  • Deactivated charge timer (12V reconnect can re-activate timer)
  • Held plug button down while plugging in OEM cord with all-green lights & the key "on"
THEN with OBD connected you can clear all the codes in every module you can access, especially the OBC, BPCM, & EVCM which are all in the Battery Management section of AlfaOBD. Be careful to turn the key from "off" only ONE click before connecting OBD, never turn it further, or it may think the "engine" is running & therefore fail to clear. Make sure to follow any other onscreen instructions carefully. They're different, for different error codes.

Any codes that aren't just false alarms will either fail to clear, or will return rapidly. AlfaOBD shows on-screen descriptions for the codes, so it you get one for the OBC that won't go away, it should be a pretty safe bet that it's the issue.
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Also, when working on the high voltage, is it sufficient to pick out the fuse under the back seat? Or is further isolation required?
Please read the service technician training manual here:


It's not a wired type, which I will not risk using.
Appreciate all the input @Electric Tire Shredder, do you have any advise on the error codes? Should I be able to determine a failed obc?
AlfaOBD shows on-screen descriptions for the codes. If all the codes stay clear except for one or more that say they're for the OBC, then it should be a pretty safe bet that your OBC has failed.

The OBD reader might not work if it isn't 1 of the following:
  • Veepeak
  • Konnwei KW902
  • OBDLink LX or MX+
  • OBDKey
  • Kiwi 3

You wrote "Think I have tried all measures in the refereed post.", but you skipped the part about OBD.

Every step is critical, & often the codes don't clear if you miss one step, so please confirm whether or not you did the following:
  • Left the humidity sensor continuously unplugged (leave it unplugged at least until all issues are resolved)
  • Simumtaneously disconnected both the 12V & the HV, & left them both disconnected for over 30 hours
  • Deactivated the car's onboard charge timer (It can reactivate itself when the 12V is reconnected)
  • With "ready" on the car's screen, confirm all green lights on the OEM charge cord, & hold down the J1772 button while plugging into the car.
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Yes to 1, 2 and 3. Do not have the oem charger
Having a hard time to believe this will sort it?

Ref obd, I have tried a few Bluetooth adapters which has not been able to connect.
Have a kw902 on order, in any case.

Clearing codes with this would relieve the need for oem charger?
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Yes, hard to believe the OEM cord could fix it, & it's possibly just a coincidence, but here's what happened to me:

I stopped to charge at a public plug on my way home & my car showed charging system failure. I proceeded to the next station on my route & it showed the same thing. I went to the final station & it showed the same too. I went home, plugged in my OEM cord & it was fine ever since.

TWO other forum members have reported similar experiences.
Your obcm is shot, i has the same goal posts. . It was 1900 to fix it here
At mckevitt fiat in Berkeley ca.
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Ya, same goal posts and same driving fine even though the car thinks it's plugged in when it's not AND same time occurring right after the power supply went off & then on.

It's still worth confirming, by checking for an OBC error code that won't stay clear.
Read the codes today, only remaining and persisting code is the humidity sensor which has been disconnected.
Plugged in to see if anything cameup, but no.

Further down you can see a few code from the very first reading. (Different OBD)

Best guess now is a blown OBC i guess. Have a second hand now, will go for this and replace.

Does anyone know if any further isolation is needed before uncoupling the OBC, than making sure connectors are disconnected before taking out fuse and disconnect 12v?

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Best guess now is a blown OBC i guess.
That would be my own best guess too, but it seems a bit strange if there are no error codes at all, besides the unplugged sensor.

There should at least be one persistent OBC code, &/or at least one false alarm code. Those are extremely common in a 500e, & they sometimes prevent operation, but only until they're cleared with AlfaOBD.

Before ripping it apart I would check with the free AlfaOBD "demo" app, which can specifically check the OBC for errors, as well as the BPCM, PIM, Body Computer, etc.
Are yo seeing my pictures @Electric Tire Shredder ? OBCM is scanned specifically without finding errors. This goes for the rest of the modules apart from BCM which states an error for humidity sensor.
Do you believe alfaobd will show errors that the pro obd tool does not?

Also note that the two pics at the bottom shows alarm present at first diagnosis. These never came back after resetting.

A local guy in Norway, Carstech Electronics AS, which have repaired several of these units claims that there usually are no specific error codes for OBCM when these fails.
This can be an indication of OBCM error, but no guarantees. He has seen cases where the battery pack has failed when failing to charge but car is still drivable.
He carries out repairs at 1500 USD. Replacing failed parts with more robust one.
I am seeing the pictures, but I'm not familiar with either of the apps shown. In AlfaOBD you need to "enter" a module to scan, which doesn't appear to have been done in the pictures. That may not be necessary with that app, however I can't be sure. That brings me back to the point that it's worth at least trying AlfaOBD before spending $1500 to replace a part that shows no errors.

He has seen cases where the battery pack has failed when failing to charge but car is still drivable.
He carries out repairs at 1500 USD. Replacing failed parts with more robust one.
So there's a non-OEM part available?!

I wonder if there's some language translation error there, or here:

I can't think of any part of the battery pack which can fail without preventing the car from driving. If a cell fails, there's no power for the motor. If a contactor fails, the battery can't power the motor. If the BPCM fails, I'm pretty sure the car also won't drive.

The top text on very first picture says onboard charger module is examined, with no errors.
I'm waiting for the kw902 and will check with alfaobd too, just to verify.

Ref non oem, I'm referring to components, which he claimed are proned to failure. But within the oem obc. Hope that clarifies.

Ref battery issue and drivable, I did not get specifics. He just mentioned that he has seen it.
I don’t think the power failure is the sole cause. Has to be from use as well. We have had dozens of power failures here this winter a lot in middle of night during charge time. And no problems. Fyi. Just a personal observation
OH! Maybe he means he's seen cars that drove but wouldn't charge showing pack failure on OBD!

Mine showed pack failure & I didn't even know it! I just happened to check out of curiosity, since the car operated perfectly. That means what it shows can be a false alarm, so I still don't get his point.

But I think I get the other part: Instead of replacing the entire bad OBC, he repairs it by replacing the fried internal components with better ones. That sounds great!

& I guess I should have said I can see the pics, but not all that well, even trying to zoom in, but I achieved my goal of getting you to check with AlfaOBD, just to verify. :)
dozens of power failures here this winter a lot in middle of night during charge time. And no problems.
That's likely just luck, since not every blackout or breaker off/on causes a big enough voltage spike to kill electronics:
  • Even a brand new OBC could die if there happens to be a big enough spike.
  • Even a really old OBC would survive if the spike happens to be small enough.
Also, just being plugged in without even charging seems to be all it takes: I was PM'ed about a charging failure in Fresno right after a breaker off/on when the car wasn't even charging.
Latest update is that I've gotten my hands on a second hand unit, confirmed working. About 600usd.
Have picked the old one out. Just waiting to receive the "new" one to put in. 👍
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