P0CE9: Hybrid/EV Electronics Coolant Pump A Control Circuit/Open

The hybrid controller checks the control line of the electric pump that moves coolant through the power electronics loop, which in GM's Volt and ELR serves the inverter module and the high-voltage charger. GM tables from 2011 to 2016 fail it when the output driver reports an open line or a short to ground or voltage in 16 of 20 samples at 250 ms. The 2019 HPC2 table measures line current instead: below 200 mA or above 3 A while the pump is commanded on, below 120 µA while it is off, for 4 s within a 5 s window. All variants are Type B, two trips. Audi logs P0CE900 on the e-tron and Q8 e-tron in thermal management unit 00C5. P0CEB and P0CEC split the fault into low and high, P0CEA covers pump function. With the pump idle, inverter and charger heat up and power is reduced.

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

Malfunction indicator lamp or hybrid/drive system warning on
Reduced drive power because inverter and charger temperatures rise
Charging power reduced or charging interrupted
Pump not audible after switch-on when commanded via scan tool

Most likely causes

Open or chafed control wire, or corroded connector at the electronics coolant pump
Failed electronics in the pump itself, drawing no current or far too much
Coolant loss from a damaged hose letting the pump run dry (Audi e-tron/Q8 e-tron bulletin)
Faulty output driver in the hybrid or thermal management control module

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
Check the continuity of the wire between the component and the control module.
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 P0CE9 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
C: Subsystem depends on the code range
E9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0CE9?

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 P0CE9?

The most common causes are: open or chafed control wire, or corroded connector at the electronics coolant pump; failed electronics in the pump itself, drawing no current or far too much; coolant loss from a damaged hose letting the pump run dry (Audi e-tron/Q8 e-tron bulletin).

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.