U027A code meaning
Lost Communication With Battery Charger Control Module C
What U027A means
Module C is a third on-board charger in the same vehicle; A and B have U019B and U01BB. Several chargers on one bus need clearly separated roles, and a Lear patent shows one way: each unit reads a coded input at start-up, then joins the vehicle bus either as master with the master message set or as slave with the slave set. A slave whose input or wiring is wrong can thus vanish from the network. U027A is stored when the supervising controller stops hearing charger C. No manufacturer documents the code publicly or names a third charger. For plug-in hybrids CARB only asks for detection of charger faults that stop charging or reduce the charging rate. AC charging then usually runs slower; driving and emissions are not affected.
U027A 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 U027A
- Reduced AC charging power or longer charging time
- Charging fault message
Common causes of U027A
- Most likely12 V supply or wake-up line of charger C missing
- PossibleBus connector at charger C corroded or not latched
- PossibleCharger C coded or addressed wrongly after replacement
- Less likelyCharger C control electronics 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 U027A means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7A | The exact fault in that area. |
What to do next
- Note U027A 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 U027A
What does U027A mean?
U027A means "Lost Communication With Battery Charger Control Module C". Module C is a third on-board charger in the same vehicle; A and B have U019B and U01BB. It is a generic code, so it means the same on every make.
Is it safe to drive with U027A?
U027A does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U027A fail an emissions test?
U027A 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 U027A to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U027A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.