P0C4B: Hybrid/EV Battery Pack Coolant Pump A Supply Voltage Circuit/Open
The HV battery pack coolant pump A reports a supply voltage circuit/open condition. Battery thermal management may be impaired.
What P0C4B means
P0C4B is a generic OBD-II powertrain code in the hybrid & EV group. In plain English: the computer found an electrical fault in that circuit: an open, short or bad connection, or a failed component.
- 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
- 01Open in supply wireMost likely
- 02Supply fuse blownPossible
- 03Pin pushed back out of connector bodyLess likely
Can I drive with P0C4B?
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 P0C4B
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P0C4B. 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 high-voltage battery pack coolant pump a 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: Open in supply wire; supply fuse blown; pin pushed back out of connector body. 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.
P0C4B 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
- Hard
- Good DIY job?
- Usually a shop job
Involved testing or major parts. Most owners use a shop.
Parts and systems involved
- High-voltage battery pack coolant pump A
- Wiring harness
- BMS
P0C4B FAQ
What does P0C4B mean?
P0C4B means “Hybrid/EV Battery Pack Coolant Pump A Supply Voltage Circuit/Open”. The HV battery pack coolant pump A reports a supply voltage circuit/open condition. Battery thermal management may be impaired.
Is P0C4B serious? Can I keep driving?
We rate P0C4B 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 P0C4B?
The most common causes, from most to least likely: Open in supply wire; Supply fuse blown; Pin pushed back out of connector body. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P0C4B?
Typical labor is about $250–$875 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 P0C4B myself?
DIY difficulty is hard. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P0C4B 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.