P0A9FHybrid/EV Battery Temperature Sensor A Circuit Intermittent/Erratic
- 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
- Cell temperature changes slowly, so a reading that jumps back and forth points to the circuit, not the battery. GM monitors this by summing the absolute sample-to-sample change of sensor A over a 10-sample window every 100 ms; if the sum exceeds 10, that window fails, and four failed windows out of five set P0A9F as Type B (two trips) in the 2016 and 2019 hybrid tables (16OBDG02, 19OBDG02). GM names a loose or intermittent connection as the typical trigger. The signal may still sit inside its valid range, which separates P0A9F from the hard low/high codes P0A9D/P0A9E and from the plausibility code P0A9C. The car protects the pack by limiting power and may show the fault only now and then.
- What you may notice
- Warning light that comes and goes
- Temporarily reduced hybrid or EV power
- Battery temperature value jumps in the scan tool data
- Likely causes
- LikelyLoose, fretted or corroded pin in the sensor connector
- PossiblePartly broken sensor wire that opens with vibration or heat
- RareElectrical interference on the sensor line from high-voltage components
- 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: €100 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.