Hybrid Battery Power Off Circuit High
The P0A29 code means the vehicle's onboard diagnostic system has detected: Hybrid Battery Power Off Circuit High. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $600 (typically wiring, a connector, or the power-off/switch circuit itself)
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Common Symptoms
- Check Engine Light and hybrid system warning on
- Hybrid system may not shut down cleanly, or may not power up
- Possible 12V battery drain if the system cannot power off properly
Probable Causes (Ranked by Likelihood)
- Wiring or connector fault in the hybrid battery power-off circuit High
- Failed switch/relay in the power-off path Moderate
- Battery control module sensing fault Moderate
Frequently Asked Questions
What does P0A29 mean?
P0A29 concerns the circuit the battery control module uses to disconnect and power down the hybrid battery safely.
Can I keep driving with P0A29?
Short distances. A power-off circuit fault can interfere with the safe connect/disconnect sequence of the HV battery - have it looked at promptly.
Is P0A29 safe to work on myself?
This code involves the high-voltage system. Do not open the HV battery, inverter, or any orange-cabled component without hybrid-specific training, insulated gloves, and the service plug removed. Diagnosis beyond a scan-tool read belongs at a hybrid-qualified shop.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Read the code and check whether it sets at power-up, power-down, or both.
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Inspect the power-off circuit wiring and connectors per the OEM diagram.
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Verify clean system shutdown: after powering off, confirm no modules stay awake draining the 12V battery.
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Follow the OEM pinpoint test for the battery control module's power-off circuit.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- Toyota/Lexus hybrids (Prius, Camry Hybrid, RAV4 Hybrid)
- Ford/Lincoln hybrids (Escape, Fusion, C-MAX)
- Honda hybrids (Insight, Civic Hybrid, Accord Hybrid)
- Hyundai/Kia hybrids and plug-in hybrids
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