What Does P0B3A Mean?
The powertrain control module has detected a high voltage condition on the motor electronics coolant pump "B" control circuit. The signal voltage exceeds the expected range, indicating an open feedback circuit, a short to battery voltage in the wiring, or a failed pump driver that is stuck in the on state.
Safety Warning
Do not drive. Without proper coolant pump control, the motor electronics may overheat rapidly, causing component damage and potential fire risk.
Common Causes
35%
Open circuit in the pump feedback or control wire causing the signal to float high
25%
Short to battery voltage in the control circuit from chafed wiring
25%
Failed coolant pump B with open internal circuit causing no current flow and high voltage on the driver
15%
PCM pump driver circuit stuck high or failed open
Diagnostic Steps
1
Step 1: Measure voltage at the coolant pump B control circuit with KOEO. Identify whether the high voltage is on the control line or feedback line.
2
Step 2: Disconnect the pump connector and recheck the control circuit voltage at the PCM. If voltage normalizes, the pump has an internal open circuit.
3
Step 3: Inspect the wiring harness for shorts to 12V power. Check routing near battery cables, fuse box, or other power sources.
4
Step 4: Test the pump motor for continuity. An open reading confirms a failed pump motor.
5
Step 5: If wiring and pump test normal, the PCM driver circuit may have failed. Check for TSBs regarding PCM updates before replacement.
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
The powertrain control module has detected a high voltage condition on the motor electronics coolant pump "B" control circuit. The signal voltage exceeds the expected range, indicating an open feedback circuit, a short to battery voltage in the wiring, or a failed pump driver that is stuck in the on...
The most common cause of P0B3A (Motor Electronics Coolant Pump "B" Control Circuit High) is: Open circuit in the pump feedback or control wire causing the signal to float high
Typical repair costs for P0B3A range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Do not drive. Without proper coolant pump control, the motor electronics may overheat rapidly, causing component damage and potential fire risk.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B3A to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Thermal Management System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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