Faulty engine coolant temperature sensor with an internal intermittent connection; Corroded, loose, or chafed wiring at the ECT sensor connector or along the harness; Coolant level low enough to expose the sensor tip, causing erratic readings; Thermostat stuck open or a cooling system air pocket that makes the temperature signal swing; Poor ground connection at the engine block or sensor return circuit; Damaged pins or terminals in the ECT sensor pigtail; Rarely, a failing powertrain control module (PCM) driver on the sensor circuit

DTC codes / Chrysler codes / P1116

P1116 · ChryslerECT Signal Unstable Or Intermittent

Q: What does code P1116 mean?

ECT Signal Unstable Or Intermittent. P1116 on a Chrysler vehicle means the engine computer has seen the engine coolant temperature (ECT) sensor signal jump around or drop out intermittently instead of changing smoothly as the engine warms up. The computer compares the coolant temperature reading against a model of how fast the engine should warm up and flags the code when the signal is unstable or erratic.

P1116 on a Chrysler vehicle means the engine computer has seen the engine coolant temperature (ECT) sensor signal jump around or drop out intermittently instead of changing smoothly as the engine warms up. The computer compares the coolant temperature reading against a model of how fast the engine should warm up and flags the code when the signal is unstable or erratic.

SystemPowertrain

Code typeChrysler specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Often no symptoms besides the warning light, especially if the glitch is brief
Temperature gauge needle that jumps, drops, or reads cold after the engine is warm
Poor fuel economy or a rich-running condition because the computer thinks the engine is still cold
Rough idle or hesitation when the engine is cold
Cooling fan running constantly or not coming on when it should
Hard starting or a longer crank time in cold weather

Common causes, most likely first

Faulty engine coolant temperature sensor with an internal intermittent connection
Corroded, loose, or chafed wiring at the ECT sensor connector or along the harness
Coolant level low enough to expose the sensor tip, causing erratic readings
Thermostat stuck open or a cooling system air pocket that makes the temperature signal swing
Poor ground connection at the engine block or sensor return circuit
Damaged pins or terminals in the ECT sensor pigtail
Rarely, a failing powertrain control module (PCM) driver on the sensor circuit

How to diagnose and fix it

Check coolant level and inspect for leaks or air pockets in the cooling system
Inspect the ECT sensor connector and wiring for corrosion, looseness, or chafing
Back-probe the ECT signal wire and watch live data on a scan tool while wiggling the harness
Compare the ECT reading cold and hot against a known-good value or an infrared thermometer
Test the ECT sensor resistance with a multimeter and compare to the Chrysler specification for that temperature
Check the sensor ground circuit for excessive voltage drop
Replace the ECT sensor if resistance is out of spec or the signal drops out during the wiggle test

What a jumpy coolant reading really means

A low coolant level is a common cause of P1116 on Chrysler vehicles because the sensor tip can be exposed to air, making the temperature signal swing wildly even though the sensor itself is fine.
Technicians often replace the ECT sensor only to find the real problem is a chafed wire near the exhaust manifold or a corroded pin in the connector that only acts up when the engine bay is hot.
P1116 does not always mean the sensor has failed; a sticking thermostat or an air pocket from a recent cooling system service can create the same unstable signal pattern.
The code can set intermittently and clear itself, so a scan tool that records freeze-frame data is more useful than a simple code reader for catching the fault in the act.
On some Chrysler models the ECT sensor shares a ground with other sensors, so a bad ground can set P1116 along with other sensor codes that seem unrelated.

Can I keep driving with P1116?

You can usually drive the vehicle short distances to a repair shop, but avoid long trips or heavy load because an unstable coolant signal can cause the computer to run the engine rich and may affect cooling fan operation. If the temperature gauge is jumping into the red or the engine is overheating, stop driving and have it towed.

Tools that help

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Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.