What it means
The control module detects high voltage in the supply circuit for electric/auxiliary transmission fluid pump A motor.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Auxiliary transmission-fluid pump A uses a powered motor to circulate fluid and support transmission hydraulic pressure. The control module sets P0B0B when voltage on the pump A supply circuit is higher than expected, which can indicate a feed shorted to power or a source or control fault.
Common causes
Most likely first.
- Supply wire shorted to voltage
- Supply voltage source or control fault
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save freeze-frame data and check related pump A and system-voltage codes to determine when the high reading was detected.
- Use scan-tool data to compare pump A supply voltage with system voltage and note whether the pump was commanded on.
- Inspect pump A supply wiring and connectors for damage, poor repairs, or contact with another powered wire.
- Test the supply circuit for a short to voltage and verify the control output using the manufacturer’s test procedure and specification.
- If the wiring is not shorted, test the supply source and pump control electronics for an erroneous high output.
Common fixes
- Repair supply wiring shorted to another voltage source.
- Correct damaged or incorrectly connected pump A terminals.
- Repair the faulty supply source or circuit connection.
- Replace or repair the pump control module if testing confirms it is driving the supply high.
Can I keep driving?
A supply fault can make pump A operation unreliable and lead to limited transmission operation. Avoid a long trip or heavy load, and stop safely if shifts become harsh, delayed, or slipping.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.