P0A99: Hybrid/EV Battery Pack Cooling Fan 2 Control Circuit Low
The HV battery pack cooling fan 2 reports a control circuit low condition. Battery thermal management is impaired.
What P0A99 means
P0A99 is a generic OBD-II powertrain code in the hybrid & EV group. In plain English: the computer sees a voltage on that circuit that is lower than it should ever be — often a short to ground, an open, or a failed sensor.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Yes
- Drive cycle to clear
- Not required
Get it fixed
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Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
Common causes
- 01Wire shorted to groundMost likely
- 02Internal motor shortPossible
- 03Connector pins corroded - high contact resistanceLess likely
Can I drive with P0A99?
Have it checked before relying on the car.
High-voltage faults can shut the drive system down without much warning. Do not open orange high-voltage components; this needs a trained technician.
Why we rate it urgent
- High-voltage system fault: the car may shut down or refuse to start
- Can put the vehicle in limp mode (reduced power)
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P0A99
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P0A99. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Test the circuit
Inspect the wiring and connector at the hybrid battery cooling fan 2 and wiring harness for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Wire shorted to ground; internal motor short; connector pins corroded - high contact resistance. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P0A99 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Usually a shop job
Needs a scan tool and some experience with testing.
Parts and systems involved
- Hybrid battery cooling fan 2
- Wiring harness
- BMS
P0A99 FAQ
What does P0A99 mean?
P0A99 means “Hybrid/EV Battery Pack Cooling Fan 2 Control Circuit Low”. The HV battery pack cooling fan 2 reports a control circuit low condition. Battery thermal management is impaired.
Is P0A99 serious? Can I keep driving?
We rate P0A99 as urgent severity. Have it checked before relying on the car. High-voltage faults can shut the drive system down without much warning. Do not open orange high-voltage components; this needs a trained technician.
What causes P0A99?
The most common causes, from most to least likely: Wire shorted to ground; Internal motor short; Connector pins corroded - high contact resistance. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P0A99?
Typical labor is about $65–$375 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P0A99 myself?
DIY difficulty is moderate. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P0A99 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.