What it means
The HV battery pack coolant pump A reports a supply voltage circuit low 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 depends on its supply-voltage circuit for operating power. P0C4C sets when the module detects that this supply is low, which can happen if the wire is shorted to ground, the supply rail is weak, or corroded connections create excessive resistance.
Common causes
Most likely first.
- Supply wire shorted to ground
- Supply rail collapsed
- Connector pins corroded - high contact resistance
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 codes, then review pump A's requested status and any available supply-voltage reading in live data.
- With the vehicle powered down as specified by the manufacturer, inspect pump A's supply connector for corrosion, looseness, heat damage, or moisture.
- Trace accessible supply wiring for insulation damage or contact with ground that could pull the supply low.
- Measure voltage drop and supply voltage at the manufacturer's specified test points while the circuit is loaded as directed by the service procedure.
- If the supply wire and connections are sound, check the supply source and pump A for a fault that is collapsing the rail.
Common fixes
- Clean and secure a corroded or loose supply connection.
- Repair supply wiring shorted to ground.
- Repair high-resistance or damaged connector terminals.
- Repair the supply source or replace pump A if testing confirms it is pulling the rail low.
Can I keep driving?
Limit driving and avoid charging or heavy loads because low pump supply can reduce battery cooling. Stop if a battery-temperature warning appears or the vehicle enters reduced-power mode.
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.