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U0116 Lost Communication With Coolant Temperature Control Module

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U0116 means a module no longer hears the coolant temperature control module, a separate controller for engines with electronically managed cooling. Depending on the design it may command electric pumps, map-controlled valves or fans and pass coolant status on to the engine controller. No manufacturer documents this code publicly; its companions P25AF (MIL request from that module) and U0456 (invalid data from it) are likewise known only from code lists. The basis is CARB's rule that missing communication from a digital input gets its own code, plus the general principle that electronic engine controls cut power when temperature control is uncertain. Expect a temperature or cooling warning and, as a precaution, reduced engine output.

Likely causes

Cooling module without power or ground (fuse, relay, ground point in the engine bay)
Heat-damaged or corroded connector near the engine
Damaged CAN or LIN wiring to the module
Coolant temperature control module internally faulty

Symptoms

  • Engine temperature or cooling system warning
  • Cooling fan or electric pump running continuously
  • Reduced engine power as protection

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–1,200
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

coolant temperature modulecan bus wiring

Related codes

U0456P25AFU0100

References: law.cornell.edu, en.wikipedia.org.