Diagnostic trouble code U0672 indicates a loss of communication between the engine control module (ECM) and the engine coolant pump. This pump is typically an electric unit that communicates over a network (e.g., LIN bus) to regulate coolant flow. The code does not necessarily mean the pump has failed; it can be triggered by wiring issues, low voltage, or a faulty pump controller.
The pump's internal electronics may have failed, preventing it from communicating on the network. This is a common failure point on vehicles with electric coolant pumps.
Open, shorted, or corroded wires in the pump's power, ground, or communication circuit can interrupt the signal. Connector pins may be loose or backed out.
A weak battery or failing alternator can cause voltage drops that disrupt network communication, including the coolant pump's LIN bus.
Although rare, a failed ECM can lose communication with the pump. This should only be considered after thoroughly testing all other components and circuits.
It depends. If the coolant pump is not operating, the engine may overheat, especially in stop-and-go traffic or hot weather. It is safest to have the issue diagnosed and repaired before extended driving.
No. While a failed pump is a common cause, wiring issues, poor connections, or low battery voltage can also trigger this code. Proper diagnosis is needed to avoid unnecessary pump replacement.
Almost never. The ECM is the least likely cause of a U0672 code. Replacing the ECM without verifying all other components and circuits is a common misdiagnosis and waste of money.
LIN (Local Interconnect Network) is a low-speed serial communication protocol often used for smart actuators like electric coolant pumps. U0672 indicates a loss of communication on that bus, which could be due to a fault in the pump, wiring, or the LIN master (usually the ECM).