What it means
The controller cannot drive the second auxiliary transmission fluid pump.
At a glance
- Usually lights the check-engine light
How it works
Auxiliary pump B supplies additional transmission fluid flow when requested, and the TCM monitors whether its motor circuit responds. This code sets when the controller detects an open circuit and cannot drive pump B.
Common causes
Most likely first.
- Open pump motor winding
- Broken control wire
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 review transmission codes and live pump B command status to establish when the circuit failed.
- Inspect pump B's connector and harness for a disconnected plug, broken wire, corrosion, or damage near the transmission.
- Check the pump B motor winding for continuity using the manufacturer's procedure to identify an open motor.
- With the pump disconnected, test the control wire and its connections for continuity from the TCM to pump B.
- If the motor and wiring test good, check the TCM connector and output for an open connection or failed driver.
Common fixes
- Reconnect and secure the pump B connector.
- Repair a broken pump B control wire or damaged terminal.
- Replace pump B if its motor winding is open.
- Repair the TCM connection or replace the TCM if its output is confirmed faulty.
Can I keep driving?
Avoid driving if shifting is slipping, shuddering, harsh, or delayed, because inadequate fluid flow can worsen transmission damage. If shifts seem normal, keep trips short and have the fault diagnosed promptly.
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.