P0A29Hybrid/EV Battery Power Off Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0A29 is stored when the voltage on the hybrid battery power-off line sits above its plausible range for longer than allowed, which points to an open line pulled up internally or a short to a supply voltage. No manufacturer explains P0A29 publicly; GM merely names it as a keyword in a generic bulletin on terminal fit. The circuit itself is the hardwired disconnect path that patents describe beside the CAN crash message, and CARB 1968.2 requires monitoring of hybrid components relevant to emissions. Related: P0A28 for a signal too low, P0A27 when the contactors do not follow the command. A stuck-high line can keep the system from powering up or from shutting down correctly.
- What you may notice
- Hybrid system warning light
- Vehicle does not reach ready mode
- High-voltage system stays active after switching off
- Likely causes
- LikelyOpen power-off line or unplugged connector
- PossiblePower-off line shorted to battery voltage
- PossibleSpread or corroded terminals at the connectors
- RareFaulty input or driver stage in the control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.