A discharged or failing 12-volt battery, or poor battery terminal connections, causing low voltage on the CAN bus; Corroded, loose, or damaged wiring and connectors at the coolant pump control module or along its CAN circuit; A failed engine coolant pump control module, including internal faults that prevent it from transmitting on the bus; A shorted or open CAN data line (CAN high or CAN low) between the pump module and the rest of the network; A faulty ground connection for the coolant pump control module, leading to intermittent or total loss of communication; Aftermarket accessories or improper electrical repairs that introduce noise or faults on the CAN bus; A software or configuration issue in a module that disrupts normal bus messaging, though this is less common

DTC codes / U01xx · Lost communication with a control module / U019F

U019FLost Communication With Engine Coolant Pump Control Module

Q: What does code U019F mean?

Lost Communication With Engine Coolant Pump Control Module. U019F is a network communication code indicating that one or more control modules on the vehicle's controller area network (CAN) bus have stopped receiving messages from the engine coolant pump control module. The computer detects this when the expected periodic CAN frames from that module are missing for a calibrated time, not when the pump itself has necessarily failed.

U019F is a network communication code indicating that one or more control modules on the vehicle's controller area network (CAN) bus have stopped receiving messages from the engine coolant pump control module. The computer detects this when the expected periodic CAN frames from that module are missing for a calibrated time, not when the pump itself has necessarily failed.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaLost communication with a control module

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) or a message on the driver information center
The engine may enter reduced power or limp mode because the powertrain control module cannot verify coolant pump operation
Overheating or a temperature warning if the pump is actually inoperative, though this is not guaranteed
No noticeable drivability change in many cases, with the warning light being the only clue
A cooling fan that runs continuously or not at all due to lost coordination with the pump module
Other unrelated modules may show communication codes if the fault is a shared bus issue

Common causes, most likely first

A discharged or failing 12-volt battery, or poor battery terminal connections, causing low voltage on the CAN bus
Corroded, loose, or damaged wiring and connectors at the coolant pump control module or along its CAN circuit
A failed engine coolant pump control module, including internal faults that prevent it from transmitting on the bus
A shorted or open CAN data line (CAN high or CAN low) between the pump module and the rest of the network
A faulty ground connection for the coolant pump control module, leading to intermittent or total loss of communication
Aftermarket accessories or improper electrical repairs that introduce noise or faults on the CAN bus
A software or configuration issue in a module that disrupts normal bus messaging, though this is less common

How to diagnose and fix it

Perform a battery and charging system test, including load testing and checking terminal cleanliness and tightness
Use a scan tool to read all modules for communication codes and record which modules are online and which are missing
Visually inspect the coolant pump control module connectors and harness for corrosion, chafing, or loose pins
Measure CAN bus voltages and resistance at the diagnostic link connector (DLC) to confirm bus integrity before condemning any module
Check powers and grounds at the coolant pump control module connector with a multimeter under load
If bus and wiring tests pass, substitute a known-good coolant pump control module or perform a module communication test as specified by the manufacturer
After repair, clear codes and verify that the pump module reports online and that no communication codes return during a road test

Why the pump module goes silent on CAN

A weak battery is the most common root cause of U019F on vehicles that sit for long periods, because low voltage can drop the pump module offline without any physical fault in the module itself.
Technicians often replace the coolant pump control module only to find the real problem is a corroded ground stud or a chafed CAN wire near the pump, so always verify bus integrity first.
U019F does not always mean the coolant pump has stopped working; the module can still drive the pump locally while failing to broadcast status on the network.
A single failed module on the CAN bus can sometimes disrupt communication for other modules, so look for multiple U-codes that may point to a shared power or ground issue rather than the pump module alone.
Aftermarket remote starters or alarm systems tapped into the CAN bus are a frequent source of intermittent communication faults that set U019F and similar codes.

Can I keep driving with U019F?

If the engine temperature gauge remains normal and there is no overheating warning, you can drive the vehicle to a repair shop, but avoid heavy loads, long trips, and stop-and-go traffic until the fault is diagnosed. If the temperature gauge climbs or a red overheating message appears, pull over safely and shut the engine off immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.