P0C4C: Hybrid/EV Battery Pack Coolant Pump A Supply Voltage Circuit Low

P0C4C reports that the supply voltage reaching battery coolant pump A is below the expected level while the circuit is not fully open. Typical reasons are high resistance in the feed, a corroded fuse contact, a weak relay, a poor ground or a short to ground that drags the line down. No manufacturer documents P0C4C publicly. Ford uses the sibling P0C4B for the open supply circuit on its 2020 Escape, Explorer and Aviator hybrids, and Bentley's bulletin on P0C4700 for 2025–2026 Continental GT and Flying Spur hybrids shows what such a feed contains: a 10 A fuse, a relay and a harness route that can chafe at the rear suspension. CARB requires the electrical parts of battery thermal management to be monitored. A pump that receives too little voltage runs slowly or not at all.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

MIL or hybrid or EV warning
Coolant pump running slowly or intermittently
Battery power reduced when the pack warms up

Most likely causes

High resistance from corroded fuse, relay contacts or connector
Poor pump ground connection
Supply wire chafed and shorted to ground

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
With the connector unplugged, check whether the signal wire is making contact with ground.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P0C4C means

P: Powertrain: engine and transmission
0: Generic code: same on every make
C: Subsystem depends on the code range
4C: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C4C?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0C4C?

The most common causes are: high resistance from corroded fuse, relay contacts or connector; poor pump ground connection; supply wire chafed and shorted to ground.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.