Damaged wiring, chafing or short to a voltage supply in the power off or shutdown control circuit; Corroded, loose or contaminated connectors at the battery pack, battery control unit or hybrid control unit; Fault in the high-voltage battery contactor or relay, or its drive circuit; Fault in the battery management or hybrid control unit that misreads or wrongly drives the circuit; Low or unstable 12 V supply or poor earths upsetting the control units; Water ingress or previous accident or crash damage affecting the battery pack or its harness.

P0A29

Hybrid/EV Battery Power Off Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
A: AreaHybrid propulsion
29: FaultThe specific fault in that area

What it means

P0A29 is the generic code for a high signal in the hybrid/EV battery power off circuit. The hybrid control unit monitors the circuit that commands or confirms disconnection of the high-voltage battery (such as the contactors or a shutdown line). It saw a voltage higher than expected, or a state that did not match the command given. The exact circuit and how it is monitored depend on the make, model and battery design.

Symptoms

Hybrid or EV system warning light, or malfunction indicator lamp on
Car will not go into READY mode or will not start
Reduced power or limp-home mode
Hybrid system shutting down unexpectedly while driving
Charging not starting or stopping early on a plug-in or electric model

Possible causes

Damaged wiring, chafing or short to a voltage supply in the power off or shutdown control circuitlikely
Corroded, loose or contaminated connectors at the battery pack, battery control unit or hybrid control unitlikely
Fault in the high-voltage battery contactor or relay, or its drive circuitpossible
Fault in the battery management or hybrid control unit that misreads or wrongly drives the circuitpossible
Low or unstable 12 V supply or poor earths upsetting the control unitspossible
Water ingress or previous accident or crash damage affecting the battery pack or its harnessrare

How to diagnose

Read all stored and pending codes and the freeze frame data, and note any other hybrid, battery or interlock codes
Check the 12 V battery condition and charging, as low voltage can cause false circuit faults
Check for manufacturer service information or bulletins for this model on the power off circuit
Visually inspect accessible wiring and connectors for chafing, corrosion, water, heat damage or previous repairs
Only if trained and qualified, and with the high-voltage system isolated following the manufacturer procedure, test the circuit for voltage, continuity and shorts against the wiring diagram
Check the battery control unit data for contactor status and commanded versus actual state, using a suitable scan tool
Clear the code and road test to see whether it returns, and recheck the freeze frame data

How to fix

Repair or replace damaged wiring and renew corroded or damaged connectors
Clean and secure connections and earths, and correct any water ingress
Replace a faulty contactor, relay or battery disconnect component as the diagnosis shows
Repair or replace the battery or hybrid control unit if confirmed faulty, applying any manufacturer software update that applies to this fault
Restore the 12 V battery and charging system to good condition

Can I keep driving?

Medium severity

If the car drives normally with no red warning or power loss, it can be driven carefully to a workshop soon. Stop driving and seek qualified help if the hybrid system warns of a fault, power drops, or the car shuts down. Do not work on high-voltage components unless trained.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.