Motor Electronics Coolant Pump Control Circuit Open
The P0B38 code indicates an open circuit in the control circuit of the motor electronics coolant pump. This pump is responsible for circulating coolant to cool the inverter and electric motor in hybrid/electric vehicles. An open circuit means there is a break in the electrical path, preventing the pump from operating correctly, which can lead to overheating of the motor electronics.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Overheating of motor electronics or inverter
- Reduced vehicle performance or limp mode
- Coolant pump not running when commanded
2. Most Common Causes
- Faulty engine electronics coolant pump 'B'
- Open or cut wiring in the pump control circuit
- Corroded, loose, or disconnected pump connector
- Defective pump control relay
- Blown pump circuit fuse
- Internal PCM failure in the pump control circuit
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Visually inspect the coolant pump connector and wiring for damage or corrosion.
Step 3: Test the pump's power and ground circuits using a multimeter.
Step 4: Check the pump's control signal from the ECM using a scan tool or oscilloscope.
Step 5: If circuits are intact, test the pump by applying direct power and ground; replace if it doesn't run.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. Driving with an open circuit in the coolant pump can cause the motor electronics to overheat, potentially leading to costly damage or a fire hazard. Have the vehicle towed to a repair shop.
How much does it cost to fix?▼
The cost typically ranges from $150 to $400, including parts and labor. The pump itself costs $50-$150, and labor adds $100-$250 depending on accessibility.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.