What it means
The second auxiliary transmission fluid pump is commanded on but does not run.
At a glance
- Usually lights the check-engine light
How it works
Auxiliary pump B circulates transmission fluid when extra hydraulic flow is needed, and the TCM checks whether the pump responds to its command. This code sets when pump B is commanded on but the controller detects that it is not operating as expected.
Common causes
Most likely first.
- Pump motor seized by sediment
- Cracked rotor magnet decouples drive
- Carbon or debris buildup preventing free movement
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 review pump B command and response data to see when the commanded operation failed.
- Inspect pump B's connector and nearby harness for damage, poor seating, or contamination that could interrupt operation.
- Check transmission fluid condition and look for sediment or debris that could restrict pump B, following the vehicle's service procedure.
- Test the pump B motor circuit and supply connections under command to distinguish an electrical fault from a pump that does not turn.
- If power and wiring are sound, inspect pump B for a seized rotor or a cracked rotor magnet that has stopped driving the pump.
Common fixes
- Clean and secure pump B's connector and repair damaged wiring.
- Service contamination or sediment in the fluid system if inspection confirms it is restricting the pump.
- Free or replace pump B if debris or carbon is preventing it from moving.
- Replace pump B if its motor is seized or its rotor magnet is cracked.
Can I keep driving?
Do not continue driving if shifts slip, shudder, or become harsh or delayed; a pump that fails to run can impair hydraulic control and cause further transmission damage. If the vehicle still shifts normally, limit driving and arrange prompt diagnosis.
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.