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Discussion Starter · #1 ·
Hi, My 2013 Volt developed an issue where the 12 Volt battery discharges while driving on either the battery or gas.
I'm getting a "service charging system" message along with the "red" battery symbol. Needless to say, I read the codes and have P1E00 and U1838 flagged.
While the car is on the Blink charger, the 12 volt battery voltage increases (as read at the battery with a volt meter) and seems to top off normally. The 12 volt battery also holds a charge and can even supply power for quite some time after the main battery goes low. Eventually the 12 volt battery gives up after driving over an hour with fan, lights, wipers heat etc. on. I would like to see if I can get some troubleshooting tips, hopefully from someone with system knowledge. I just switched from driving Volvos and Saabs for over thirty years and am trying my best to swear off the gas. I can fix a 9-3 but this thing has me scratching my head. I'm kinda wondering about this die cast metal box with wires, mounted under the black tray in the trunk and forward of the 12 volt battery a few feet. I has a part number 24261518. I would like to see of the two orange wires to it have current but as some wires on this car are shielded, I don't dare pierce the insulation with a prod. Trying to separate the wires seems fruitless. Maybe I should look elsewhere... cheers
 

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Fist off, do not and I mean DO NOT ever pierce any orange wires in a hybrid or EV car. These are high voltage wires, you will cause a loss of isolation issue and have to replace that wire(s). You may have a issue with your DC to DC charger, the box with the orange wires going to it near your battery. The u1838 is a comm code for the battery charger, you may try and disconnect the battery to see if this resets the problem. Also you should have the battery load tested to make sure the voltage is good and not just tested with a volt meter. Any good auto parts store car do this at no charge, just make sure they test it as a AGM battery. The diagnosis for this code has a lot of testing to make sure there is good power and ground to the module and that the comm lines are good. If every thing checks out, then replacing the DC to DC battery charger is the repair.

DTC U1838Lost Communication with Battery Charger Control Module on High Voltage Energy Management CAN Bus

There are no bulletins for this issue found.
 

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Fist off, do not and I mean DO NOT ever pierce any orange wires in a hybrid or EV car. These are high voltage wires, you will cause a loss of isolation issue and have to replace that wire(s). You may have a issue with your DC to DC charger, the box with the orange wires going to it near your battery. The u1838 is a comm code for the battery charger, you may try and disconnect the battery to see if this resets the problem. Also you should have the battery load tested to make sure the voltage is good and not just tested with a volt meter. Any good auto parts store car do this at no charge, just make sure they test it as a AGM battery. The diagnosis for this code has a lot of testing to make sure there is good power and ground to the module and that the comm lines are good. If every thing checks out, then replacing the DC to DC battery charger is the repair.

DTC U1838Lost Communication with Battery Charger Control Module on High Voltage Energy Management CAN Bus

There are no bulletins for this issue found.
 

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Discussion Starter · #5 ·
Nice and thank you for your responses. What I really need to accomplish however, is to repair my car. If anyone out there understands the low voltage charging system or can help with information on back-probing the connector on the dc-dc converter and how to obtain readings on the two orange high tension leads into the converter, please respond.
As a side note and response to a previous reply, probing through wiring insulation is at times acceptable and necessary for the sake of obtaining test results. Care must be taken to insulate oneself from the probe when performing tests on high tension wiring. Also, any resulting damage to insulation should be slight. However, minor insulation damage to an extent, regardless of the cause, be it chafing, chemical or thermal damage, can be repaired with the application of various products such as Scotch 70, shrink-fit, spiral wrap etc. The important thing is to note what it is being probed and how it is constructed as well as the potential for physical harm.
Please, if you have any substantive info on my issue with the failure to charge the 12 volt battery while driving, please respond.
The battery checked out with Delco test apparatus and thanks for the tip.

Cheers
 

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Why are you NOT using the dealer to solve this problem?

The Volt's 12V battery is being charged by an Accessory Power Module (APM) that takes power from the high voltage battery and converts it to 12 volts DC for the AGM battery.
 

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The box you're describing is the APM, the dc dc converter that sounds like the source of your problem. Is apparently not talking to the rest of the car and not providing 12V power. (The 12V is charged while the car is charging by a separate circuit in the charger module.)

Check that all the connections are tight at the APM. Probing the orange wires through the shielding is not only dangerous, but also stands a significant chance of disabling the car, since it is always checking for isolation on those wires. If you can get one at a decent price, a replacement APM would be my next suggestion.
 

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A battery can take what is referred to as a top charge and appear to be charged with a multi-meter but will run down rapidly in use.
I would say you need to replace the battery, not the dc to dc converter.
 

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Agreed. It is probably the battery.
 
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