What U029A means
The vehicle bus reports loss of communication with the high-voltage battery pack sensor module.
How the engine computer detects it
Cell-voltage and temperature data needed for state-of-charge and state-of-health calculation are missing.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
- Bus wiring open or shorted Most likely
- Module without power or ground Possible
- Module failed Possible
How to diagnose U029A
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: hv battery sensor module, vehicle bus wiring.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report U029A most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Chrysler Pacifica | 2017–2021 | 4 | — |
Counts of owner complaints to the NHTSA that mention U029A (4 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- U
- Network
- 0
- Generic (SAE) code
- 29A
- Specific fault
Questions drivers ask
Can I drive with code U029A?
It depends on which module stopped communicating. If the car drives normally, drive carefully to a shop. If the engine, transmission, brakes or steering act up, or many warning lights come on at once, stop and have it towed.
Will U029A clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Often reported together
Codes that owners mention in the same NHTSA complaints as U029A. They can point to a shared cause, so it's worth checking them together.
- P1D43Manufacturer-specific code3 complaints
- U0412Invalid Data Received from Wheel Speed Sensor (Front, Passenger Side)3 complaints
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.