What it means
The vehicle bus reports loss of communication with smart engine coolant pump (electric water pump). Pump speed cannot be commanded; coolant flow falls back to a default duty.
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
The electric engine coolant pump circulates coolant, and its controller receives pump commands and reports status over the vehicle network. The control module sets U0672 when communication with the pump is lost, so commanded speed is unavailable and coolant flow may fall back to a default level.
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 all modules for communication faults and review freeze-frame data, especially coolant temperature and whether other devices lost network contact.
- Check scan-tool data for pump communication, commanded speed, and reported status; note any coolant temperature rise or pump-related warning.
- With the engine cool, inspect the electric pump connector and harness for looseness, corrosion, coolant intrusion, or damage.
- Using the manufacturer's wiring information, check pump power and ground and test the network wires for opens, shorts, or poor connections.
- If power, ground, and wiring are intact, test communication at the pump and assess whether its control module has failed.
Common fixes
- Reconnect or clean the coolant pump connector and repair damaged wiring.
- Restore the pump's missing or poor power or ground connection.
- Repair an open or short in the network wiring to the electric coolant pump.
- Replace the pump assembly if its supplies and network wiring are sound but it remains offline.
Can I keep driving?
Treat this as urgent because reduced coolant flow can overheat and damage the engine; avoid driving if the temperature rises, a coolant warning appears, or the pump is not operating. If temperature is stable, drive only a short distance while monitoring it and stop immediately if it climbs.
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.