Code Definition

C1781 — Engine Coolant Temperature Signal Missing/Fault

System: Chassis  |  Type: Manufacturer-Specific  |  Make: Ford

About C1781

C1781 is a manufacturer-specific chassis diagnostic trouble code recorded for Ford vehicles. It belongs to the C-prefix family of codes, which covers chassis, braking, steering, suspension, or stability-control faults.

Scanning & clearing: Chassis (C) codes are stored in the ABS, traction control, or stability-control modules. An enhanced or OEM-level scan tool is usually required to read and clear them.

C1781 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

DTC C1781 is set when a module, typically the climate control or chassis module on Ford applications, fails to receive a valid engine coolant temperature signal. The coolant temperature is measured by the PCM through the engine coolant temperature (ECT) sensor and shared with other modules over the vehicle network, where it supports cabin heating strategy, temperature gauge operation, and on hybrid models the decision to run the engine for heat. The code sets when the temperature message is missing from the network or the received value is implausible. When this code is set, symptoms can inclu...

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