What Does P0C4B Mean?
The power supply circuit to the hybrid battery coolant pump has an open condition or is not providing voltage. The pump cannot operate because it is not receiving the required battery voltage supply.
Safety Warning
Without power, the coolant pump cannot operate and battery will overheat. Vehicle will enter protection mode with severely reduced power or complete shutdown, potentially stranding you.
Common Causes
40%
Blown fuse in pump power supply circuit
30%
Failed relay providing power to coolant pump
20%
Broken or disconnected power supply wire to pump
8%
Corroded or loose power connection at pump or junction
2%
Open circuit in main power distribution
Diagnostic Steps
1
Step 1: Locate and test fuse(s) for hybrid battery coolant pump power circuit
2
Step 2: Check pump relay operation by listening for click and testing relay contacts
3
Step 3: Measure voltage at pump power supply terminal with pump commanded on (should be battery voltage)
4
Step 4: Trace power supply wiring from fuse/relay to pump checking for breaks or damage
5
Step 5: Inspect all power connections and terminals for corrosion or looseness
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The power supply circuit to the hybrid battery coolant pump has an open condition or is not providing voltage. The pump cannot operate because it is not receiving the required battery voltage supply.
The most common cause of P0C4B (Hybrid Battery Pack Coolant Pump Supply Voltage Circuit/Open) is: Blown fuse in pump power supply circuit
Typical repair costs for P0C4B range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Without power, the coolant pump cannot operate and battery will overheat. Vehicle will enter protection mode with severely reduced power or complete shutdown, potentially stranding you.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0C4B to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Battery Cooling System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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