P0AC5Hybrid/EV Battery Temperature Sensor B Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- Battery temperature sensor B is one of several thermistors that measure cell or module temperature inside the high-voltage pack; GM's Volt bulletin calls it sensor 2 of nine. P0AC5 is the general circuit code for it, used for an electrical fault the controller does not classify as low, high or erratic. No manufacturer documents this exact code publicly; GM, for instance, reports P0AC6 to P0AC9 instead. CARB requires hybrid battery temperature inputs to be monitored for circuit faults. With one sensor missing the controller has a gap in its temperature picture and tends to limit charge and discharge power. The sensor usually sits on a module or sensing board inside the pack, so checks need high-voltage safety procedures.
- What you may notice
- Hybrid system or check engine warning
- Reduced electric power and regeneration
- Charging may be slower on plug-in models
- Likely causes
- LikelyPoor contact or damaged wire between sensor B and sensing board
- PossibleTemperature sensor B failed
- RareFault in the battery controller input stage
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.