What it means
The HV battery pack coolant pump A reports a supply voltage circuit/open condition. Battery thermal management may be impaired.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Battery-pack coolant pump A needs a supply voltage to operate, separate from the circuit that commands it. The module detects an open condition in the pump supply-voltage circuit for P0C4B, so pump A may not receive power and battery cooling can be impaired.
Common causes
Most likely first.
- Open in supply wire
- Supply fuse blown
- Pin pushed back out of connector body
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Save freeze-frame data and check related pump or battery-cooling codes, then use live data or a supported command to confirm whether pump A is being requested to run.
- With the vehicle powered down as specified by the manufacturer, inspect the pump supply connector for a pushed-back pin, loose fit, or corrosion.
- Check the accessible supply wire between its source and pump A for a break, chafing, or a disconnected section.
- Check the relevant fuse and supply path using the manufacturer's wiring diagram, replacing a fuse only after checking for a short or overload cause.
- Measure supply continuity and voltage at the specified test points using the manufacturer's procedure to locate the open circuit.
Common fixes
- Seat a pushed-back supply terminal correctly and secure the connector.
- Repair an open or damaged pump supply wire.
- Replace a failed fuse after identifying and correcting any cause of the failure.
- Repair corroded terminals or a poor supply connection.
Can I keep driving?
Avoid heavy loads and charging because pump A may not run without its supply, reducing battery cooling. Stop if the vehicle limits power or reports a battery-temperature warning.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.