P0116 — Engine Coolant Temperature Sensor 1 Circuit Range/Performance

Coolant temperature reported by sensor 1 does not behave plausibly. The value may be stuck or inconsistent with engine conditions. This alone does not prove a faulty thermostat; compare actual temperature with the input reaching the controller.

Affected system: Powertrain

Symptoms

• Difficult starting or unusual idle, depending on the calculated temperature.
• Higher consumption, engine warning light or a fallback fan strategy, depending on the vehicle.

Possible causes

• Corroded connector, open/shorted wiring or a failed sensor.
• Incorrect reference or ground; for plausibility faults, check actual coolant level and warm-up.

What to check

• With the engine cold, check coolant level and leaks; do not open the cap while the system is hot.
• After a complete cold soak, compare ECT with intake air and ambient temperature, allowing for location and residual heat.
• Inspect sensor 1’s connector and harness; test signal, supply and ground with the exact engine wiring diagram.
• Log engine warm-up and compare ECT with an independent measurement; separate a stuck reading from genuinely insufficient warming.
• After repair, clear codes and recheck ECT temperature under the original recorded conditions, following the manufacturer’s procedure.

Also written as: P0116-00, P011600, PO116 (some scan tools add the fault-type byte, e.g. -00).