What it means
The control module detects low 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 relies on its supply circuit to power the motor that circulates fluid for hydraulic pressure. P0B0A means the module sees supply voltage below the expected level, often from resistance or a weak connection that still allows some current to flow.
Common causes
Most likely first.
- High resistance or partial open in supply wiring
- Poor connector contact or ground
- Supply voltage source 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
- Record freeze-frame data and related codes to see whether the low supply voltage coincided with pump A operation or a broader low-voltage event.
- Check battery and charging-system data and compare pump A commanded status with available supply-voltage data.
- Inspect the pump A feed, connector, ground, and fuse connections for corrosion, looseness, heat damage, or damaged insulation.
- Measure voltage drop across the supply and ground paths while pump A is commanded on, following the manufacturer’s procedure and specification.
- If wiring and connections pass, test the supply source and pump control output to locate the voltage loss.
Common fixes
- Clean and secure corroded or loose pump A connector and ground contacts.
- Repair a high-resistance or partially open supply wire.
- Replace a damaged fuse or fuse-holder connection after correcting any underlying fault.
- Repair the supply source or pump control output if it fails the specified test.
Can I keep driving?
Low supply voltage can leave pump A unable to maintain transmission pressure, causing harsh or delayed shifts or limp mode. Keep driving gentle and brief only if the vehicle shifts normally; stop if it slips, loses drive, or the warning escalates.
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.