What it means
A control module has stopped receiving expected network messages from coolant pump B. The code indicates a communication fault; the effects depend on the vehicle's cooling system design.
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
Coolant pump B is a networked pump serving a separate or additional coolant circuit, depending on the vehicle design. U0624 sets when a control module stops receiving expected messages from pump B, so the vehicle cannot confirm or command this specific pump normally.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Warning light or message related to the affected system
- Cooling system may not operate as intended
How to diagnose it
- Scan all modules for communication codes and record freeze-frame data to see whether pump B's fault appeared with a low-voltage or network problem.
- Check live coolant temperatures and pump B command or status data, if available, and compare with pump A to distinguish which circuit is affected.
- With the engine cool, inspect pump B's connector and wiring for coolant contamination, corrosion, loose pins, or physical damage.
- Check pump B's fuse, power, and ground against the manufacturer's wiring diagram.
- Test the network circuit serving pump B for opens and shorts using the manufacturer's procedure.
- If supply and network checks pass, verify that pump B communicates and operates before replacing it.
Common fixes
- Repair damaged wiring or connector terminals at coolant pump B.
- Replace a failed fuse or restore pump B's power or ground.
- Repair an open or short in pump B's network circuit.
- Replace coolant pump B if its power, ground, and network wiring are sound but it remains offline or inoperative.
Can I keep driving?
Stop driving if the temperature gauge rises or a coolant temperature warning appears, and allow the engine to cool before checking anything under the bonnet. Pump B may serve a cooling circuit whose failure can lead to overheating and engine damage.
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.