P0B38: Motor Electronics Coolant Pump B Control Circuit/Open

Hybrid and electric drives cool the inverter and motor electronics with electric coolant pumps; J2012 numbers them A, B and C. P0B38 sets when the controller detects an open or general fault in the control line of pump B, typically by checking the driver output for missing load current. No manufacturer documents P0B38 publicly. FCA uses a pump B on the Jeep Compass and Renegade 4xe, where bulletins name its performance code P0C74, and Mercedes uses the pump A code P0A05 for an open control circuit of the low-temperature circuit pump on M264 engines. CARB requires output components of inverter thermal management to be monitored. Expect a coolant or hybrid warning and power reduction if electronics overheat.

Medium severity. Can I keep driving?Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

Symptoms

Hybrid system or coolant warning, MIL on
Reduced electric drive power when electronics get hot
Pump not running audibly after switch-on

Most likely causes

Pump connector loose, corroded or terminal pushed out
Open control wire between controller and pump
Pump electronics or motor failed open
Driver stage in the controlling module faulty

What to check, in order

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

With the engine cold, check the coolant level; never do this when the system is hot
Check the continuity of the wire between the component and the control module.
Check the actual temperature in live data
Make sure the fan comes on when it should
Check the thermostat and connector
Measure the sensor and replace it if its readings do not make sense

Good to know

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

What each character of P0B38 means

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

Frequently asked questions

Can I keep driving with code P0B38?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P0B38?

The most common causes are: pump connector loose, corroded or terminal pushed out; open control wire between controller and pump; pump electronics or motor failed open.

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.