What it means
The vehicle bus reports loss of communication with transmission fluid pump module B. Auxiliary ATF pumping during start/stop or hybrid coast cannot be commanded, which may delay shifts or impair cooling.
At a glance
- Usually lights the warning light of the system that lost communication
- The engine or gearbox may go into limp mode
How it works
Transmission fluid pump module B controls an auxiliary transmission-fluid pump for operating conditions when additional circulation is needed, such as some stop/start or hybrid coast events. The transmission controller expects messages from module B; this code sets when those messages disappear and the pump cannot be commanded through normal network communication.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan the transmission and other control modules for network, voltage, and transmission codes, and review freeze-frame data.
- Check whether transmission fluid pump module B responds to the scan tool and whether its pump status or command data is present.
- Inspect module B's connector and wiring for looseness, fluid or water entry, corrosion, and chafing.
- Test module B's power and ground under the manufacturer's specified conditions.
- With the vehicle powered down as instructed by the manufacturer, check the network wiring to module B for opens, shorts, and poor connections.
- If the module has good supplies and network wiring but is still offline, confirm failure using the manufacturer's diagnostic process.
Common fixes
- Secure a loose connector at transmission fluid pump module B.
- Repair damaged or corroded wiring and network connections at module B.
- Restore module B's power or ground supply.
- Replace module B if its circuits are sound but it still does not communicate.
Can I keep driving?
Avoid driving if the transmission shifts abnormally or a transmission warning appears, since loss of auxiliary pumping can impair fluid circulation or cooling in some conditions. If limp mode occurs, stop safely and arrange diagnosis before continuing.
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.