P1B77 on Hyundai
High-voltage battery precharging fault
Severity: Inspect soon
This is a high-voltage hybrid system fault, and the owner we read described losing drive in traffic and being towed, so treat it as a shop visit rather than a drive-and-see code.
It gets more serious if:
- Stop: Stop driving and have the car towed if the hybrid warning light is on together with loss of drive, a no-start, or the car coasting to a stop.
This page covers only what differs on Hyundai. For what P1B77 means, the ranked causes and the test order, see the P1B77 guide.
What's different on Hyundai
HyundaiYour car
2014–2017 · Sonata
Supported by vehicle data2016-2017 Sonata Hybrid: Hyundai bulletin links this code to a loose power relay assembly or cable. 2014 Sonata Hybrid complaints show it with P1B25 and a blown fuse.
2019 · Ioniq
Supported by vehicle dataThe 2019 Ioniq Hybrid has a battery management software update for this code.
20-01-003HStatus unverified
Sonata Hybrid power relay assembly and high voltage cable inspection
2016–2017sonata · NHTSA 10170894
Summary-only record: a loose connection in the power relay assembly or high-voltage cable can cause a no-start or warning lights with P1B77 and P1990; the bulletin describes inspecting and replacing the parts. We did not read the procedure.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
19-01-023HStatus unverified
Battery management software update for DTC P1B77
2019ioniq · NHTSA 10165457
Summary-only record: a battery management software update changes the diagnostic logic for this code on the Ioniq Hybrid. We did not read the procedure.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Sources and review
- Hyundai bulletin 20-01-003H: Sonata Hybrid power relay assembly and high voltage cable
- NHTSA complaint ODI 11532527: 2014 Hyundai Sonata Hybrid, codes P1B77, P1B96, P1B70, P0A0D
- Hyundai bulletin 19-01-023H: BMS software update to diagnostic logic for DTC P1B77
- NHTSA complaint ODI 11546978: 2014 Hyundai Sonata Hybrid, codes P1B25 and P1B77
- P1B77 High Voltage Battery Precharging Fault (Hyundai)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error