Motor Electronics Coolant Pump Control Circuit Low
The P0B39 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit of the motor electronics coolant pump. This pump is responsible for circulating coolant through the inverter and motor electronics in hybrid/electric vehicles. A low circuit voltage suggests a fault in the wiring, connector, or the pump itself, potentially leading to overheating of the motor electronics.
01. Most Common Causes
- Faulty motor electronics coolant pump
- Open or shorted wiring in the pump control circuit
- Poor electrical connection at the pump connector
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Overheating of motor electronics or inverter
- Reduced hybrid system performance
- Possible vehicle shutdown to protect components
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for related codes.
Step 2: Inspect the coolant pump connector and wiring for damage, corrosion, or loose pins.
Step 3: Measure voltage at the pump control circuit with a multimeter; compare to manufacturer specs.
Step 4: Test the pump by applying direct power and ground; if it doesn't run, replace the pump.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a low circuit voltage can cause the pump to fail, leading to overheating of motor electronics and potential damage to expensive components.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether the pump needs replacement or just a wiring repair.