U027B code meaning
Lost Communication With Battery Charger Control Module D
What U027B means
U027B refers to a fourth charger unit. In multi-charger designs the units also split the control task; in a dual charger system patented by Lear, two chargers feed the battery in parallel, one regulating voltage and the other regulating current. If one partner falls silent, the remaining unit has to carry the job alone or charging is stopped. U027B is set when the supervising controller loses all messages from charger D, whereas U057C stands for messages from D that arrive but fail checks. No manufacturer documents U027B or a fourth on-board charger publicly. The CARB rule for plug-in hybrids exempts charging faults that cannot be told apart from a supply problem outside the car. Expect slower or interrupted charging.
U027B at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U027B
- Charging power lower than usual
- Charging session aborted with a warning
Common causes of U027B
- Most likelyLow-voltage supply, fuse or wake-up of charger D missing
- PossibleBus wiring to charger D damaged or connector wet
- Less likelyCharger D control board faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
On board chargerVehicle bus wiring
What each part of U027B means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7B | The exact fault in that area. |
What to do next
- Note U027B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U027B
What does U027B mean?
U027B means "Lost Communication With Battery Charger Control Module D". U027B refers to a fourth charger unit. It is a generic code, so it means the same on every make.
Is it safe to drive with U027B?
U027B does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U027B fail an emissions test?
U027B is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U027B to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U027B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.