P1B25 High-voltage battery path fault

Hyundai hybrid high voltage battery path fault

P1B25 in short

On Hyundai hybrids such as the Sonata Hybrid, P1B25 means the computer found a fault in the path that carries high-voltage power from the battery. Owners report losing drive and being stranded. High-voltage parts are dangerous, so do not open them yourself; get a Hyundai hybrid-trained shop to diagnose it.

The hybrid battery feeds the motor through a high-voltage path that includes the power relay assembly and a safety plug. When the battery computer sees that path misbehave, it stores a path fault and may shut the system down to protect it.

In the one 2014 Sonata Hybrid complaint we read, a Hyundai dealer invoice listed P1B25 'high voltage path fault' with P1B77 'high voltage precharge fault' and called the power relay assembly and safety plug assembly faulty. The owner said the car lost control with four passengers and was towed.

This page covers Hyundai only. Kia owners also report P1B25 with a blown high-voltage fuse, but we did not find a second independent source for the Kia meaning, so it is not claimed here.

Pick your make

P1B25 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

Most likely causes

  1. Faulty power relay assembly or high-voltage connection

    Supported by vehicle data
    Why it ranks here
    The dealer invoice in the Sonata Hybrid complaint called the power relay assembly faulty, and a Hyundai bulletin links loose relay or cable connections to the related P1B77 code.
    What would change this
    The same power relay assembly findings are listed for P1B77 in Hyundai's bulletin; a hybrid-trained shop confirms it with high-voltage tests.

  2. Blown high-voltage fuse

    Possible — needs testing
    Why it ranks here
    One Sonata owner reported a blown 150 amp fuse with this family of codes, but that complaint does not prove the fuse was the cause rather than the result.
    What would change this
    A fuse that blows again after replacement points to a deeper high-voltage fault.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Have a Hyundai hybrid-capable shop read the hybrid battery system data and test the high-voltage path and relays.

    Best left to a shop

    Warning:Hybrid high-voltage systems can deliver a lethal shock. Only trained technicians with insulated tools and the safety plug removed should open them; never touch orange cables.

Symptoms

  • Check engine or hybrid warning light on
  • Loss of drive or coasting to a stop Gets more serious: stop and have it checked.
  • No-start Gets more serious: stop and have it checked.

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

On your vehicle

Hyundai

  • 2014 · Sonata

    Supported by vehicle data

    A 2014 Sonata Hybrid complaint quotes a dealer invoice with P1B25 and P1B77 and a faulty power relay assembly and safety plug assembly.

  • P1B77High-voltage battery precharging fault

    Shares causes Supported by vehicle data

    The dealer invoice listed P1B25 and P1B77 together on the same Sonata Hybrid, and both involve the high-voltage battery path.

All Hybrid and electric drive codes

Sources and review

  1. NHTSA complaint ODI 11546978: 2014 Hyundai Sonata Hybrid, codes P1B25 and P1B77 — NHTSA
  2. P1B25 High Voltage Battery Path Fault (Hyundai) — troublecodes.net
  3. Hyundai bulletin 20-01-003H: Sonata Hybrid power relay assembly and high voltage cable — Hyundai Motor America
  4. NHTSA complaint ODI 11532527: 2014 Hyundai Sonata Hybrid, codes P1B77, P1B96, P1B70, P0A0D — NHTSA
Last reviewed
Written by
Saurabh K.
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