U0116

Universal

Lost Communication With Coolant Temperature Control Module

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The vehicle has detected that other control systems are not receiving expected messages from the coolant temperature control module. On vehicles equipped with this module, it manages coolant-temperature-related functions; its exact role varies by vehicle. A communication loss may affect temperature readings, cooling-system operation, or related warnings, but this code alone does not prove the module has failed.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the temperature gauge rises unusually, an overheating warning appears, or you see steam or a coolant leak, stop safely and switch off the engine. Do not open the cooling system while it is hot. If there are no signs of overheating, arrange diagnosis promptly and monitor the temperature while driving.

Common Symptoms

  • The check-engine light or another warning may appear because the vehicle has detected missing module messages.
  • The coolant temperature display or related readings may be unavailable or unreliable if the vehicle depends on messages from this module.
  • Cooling-system behavior may be abnormal on vehicles where the module manages temperature-related functions.
  • The vehicle may limit some functions or enter a reduced-power mode, depending on its design and how other systems respond to the lost messages.
  • There may be no noticeable symptoms if the communication loss is intermittent or other systems continue to operate normally.

Common Causes

  • A loose, damaged, corroded, or contaminated connector or wiring connection may interrupt communication.
  • A fault in the vehicle's communication wiring or network may prevent messages from reaching the module.
  • An interruption to the module's power or ground may make it unavailable to other systems.
  • A fault within the coolant temperature control module is possible, but the code alone does not establish that the module needs replacement.
  • A problem elsewhere on the vehicle network may interfere with communication to this module.

Diagnostic Steps

  1. Check the dashboard for an overheating warning and watch the temperature display. Stop driving if the engine appears to be overheating.
  2. With the vehicle safely parked and the engine off, visually inspect accessible wiring and connectors related to the cooling system for obvious damage, looseness, or corrosion. Do not disconnect components unless the vehicle-specific service information says it is safe.
  3. Check whether the battery terminals are visibly loose or corroded. Unstable vehicle power can contribute to communication problems; follow the vehicle's instructions before cleaning or disconnecting terminals.
  4. If you have a scan tool that can read multiple modules, record all codes and note which modules do not respond before clearing anything. Related codes can help distinguish a local connection issue from a wider network problem.
  5. If the code returns, the module does not respond, or wiring checks require access to vehicle-specific circuits, have a qualified technician diagnose it using the correct service information.

When to Call a Professional

Use a scan tool capable of communicating with the vehicle's modules to check whether the coolant temperature control module responds and to review related network codes. A technician can verify the module's power, ground, connectors, and communication circuits using the vehicle-specific wiring information, then determine whether the fault is in the module, its connections, or another part of the network.

Compare component listings

Confirm diagnosis and vehicle fitment before buying. A listing does not prove that a part needs replacement. We may earn a commission from qualifying purchases.

Search Amazon Search eBay

Commonly Asked Questions

Does U0116 mean the coolant temperature control module is defective?

No. It indicates lost communication with that module, not the reason communication was lost. Wiring, connectors, power or ground, a network fault, or the module itself may be involved.

Can I drive with U0116?

It depends on whether the cooling system is operating normally. If the temperature rises, an overheating warning appears, or there is steam or a coolant leak, stop safely and switch off the engine. If there are no symptoms, arrange diagnosis and keep monitoring the temperature.

Why might there be no warning signs?

A communication fault can be intermittent, or other vehicle systems may continue to operate without noticeable changes. The stored code still warrants checking, especially if it returns.

What helps distinguish a module fault from a wiring or network problem?

A scan of all modules, checking which units communicate, and testing the module's power, ground, connectors, and communication circuits can help identify where communication is being interrupted. The exact tests depend on the vehicle.

Browse Available Code Guides

Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.