Hybrid Battery Pack Cooling Fan 2 Control Circuit Low
The P0A99 code means the vehicle's onboard diagnostic system has detected: Hybrid Battery Pack Cooling Fan 2 Control Circuit Low. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $150 - $900 (a connector or fuse at the low end; fan assembly with access labor at the high end)
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Common Symptoms
- Check Engine Light on
- Often no symptom the driver notices (per Ford TSB 16-0118)
- Battery cooling fan not responding to commands
- Pack temperatures higher than normal on a scan tool
Probable Causes (Ranked by Likelihood)
- Failed battery cooling fan motor Very High
- Open/shorted fan control wiring or a corroded connector High
- Failed fan speed controller or module driver Moderate
- Blown fan fuse Low
Frequently Asked Questions
What does P0A99 mean?
P0A99 means the control circuit for the Hybrid Battery Pack Cooling Fan 2 is open or faulty - the module cannot properly drive the fan that cools the high-voltage battery.
Can I keep driving with P0A99?
The car drives normally, which is exactly the trap: nothing feels wrong while the pack quietly runs hotter than designed. Heat shortens pack life, so fix this promptly - it is cheap prevention of a very expensive failure.
Is P0A99 safe to work on myself?
Cleaning the cabin-side battery cooling intake is generally owner-serviceable. Anything beyond that: This code involves the high-voltage system. Do not open the HV battery, inverter, or any orange-cabled component without hybrid-specific training, insulated gloves, and the service plug removed. Diagnosis beyond a scan-tool read belongs at a hybrid-qualified shop.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Command the fan with a scan tool and observe whether it responds at each speed.
-
Check power, ground, and the control signal at the fan connector.
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Inspect the connector and harness for corrosion and damage.
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While access is open, clean the fan and cabin-side intake - debris is a common companion find.
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Confirm normal pack temperatures on a road test after repair.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- Ford TSB 16-0118 (Sept 2016), 'Hybrid - Diagnostic Trouble Codes (DTCs) P0A81 and/or P0A96' - defines the battery pack cooling fan 1 and fan 2 control circuits on Escape Hybrid / Mariner Hybrid and notes the codes usually produce no symptom the driver notices.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Commonly Affected Vehicles
- Toyota Prius and other Toyota/Lexus hybrids
- 2005-2012 Ford Escape Hybrid / Mercury Mariner Hybrid
- Honda Insight and Civic Hybrid
- Hyundai Sonata Hybrid / Kia Niro Hybrid
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