Lost Communication With Coolant Temperature Control Module
The U0116 code means the vehicle's onboard diagnostic system has detected: Lost Communication With Coolant Temperature Control Module. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $50 - $600 (fuses, grounds, or wiring most often; module replacement only after the circuit tests good)
Network codes mean modules are not communicating. You need a scanner that reads all systems to find the problem.
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What Are the Symptoms of U0116?
- Check Engine or related warning light on
- The Coolant Temperature Control Module's functions may be degraded or offline
- Often stored alongside other U-codes when a whole bus segment drops
- Symptoms can be intermittent - connector and wiring faults come and go with heat and vibration
What Causes U0116? (Most Likely First)
- The Coolant Temperature Control Module has lost power or ground (check its fuses first) High
- CAN bus wiring damage - chafed harness, corroded connector, water intrusion High
- Failed Coolant Temperature Control Module no longer transmitting Moderate
- Another faulted module loading down the bus Low
Can I Still Drive with U0116?
Yes, but fix soon. U0116 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring the light.
Frequently Asked Questions
What does U0116 mean?
U0116 means other modules stopped receiving messages from the Coolant Temperature Control Module on the vehicle network. It is a communication fault - the module may be fine but unreachable.
Can I keep driving with U0116?
Usually yes for a short period. The affected function may be degraded, and intermittent wiring faults tend to worsen - diagnose soon.
Should I replace the module for U0116?
Not first. Most communication codes are power, ground, fuse, or wiring problems. Replace the module only after those test good - modules are expensive and often require programming.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose U0116?
-
Scan ALL modules - the pattern of which modules report lost communication localizes the break.
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Check the fuses and grounds feeding the Coolant Temperature Control Module before suspecting the module itself.
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If many modules are unreachable, test the CAN bus: about 60 ohms across CAN High/Low (two 120-ohm terminators) with the battery disconnected.
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Wiggle-test connectors along the affected harness while watching for the module to drop on and off.
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Only after power, ground, and bus test good should the Coolant Temperature Control Module be suspected.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Which Vehicles Commonly Get U0116?
- All OBD-II vehicles - network (U) codes are standardized across makes
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