Faulty Engine Coolant Temperature Sensor 2 internally shorted to ground; Damaged or chafed sensor wiring shorted to ground between the sensor and the PCM; Corroded, loose, or pushed-back terminal at the sensor connector or PCM connector; Open ground return circuit for the sensor, causing the PCM to read a low signal; Coolant intrusion into the sensor connector or sensor body; PCM internal fault pulling the sensor signal low (rare)

DTC codes / P21xx · Fuel and air metering / P2184

P2184Engine Coolant Temperature Sensor 2 Circuit Low

Q: What does code P2184 mean?

Engine Coolant Temperature Sensor 2 Circuit Low. P2184 means the powertrain control module (PCM) has detected a low-voltage signal on the Engine Coolant Temperature Sensor 2 circuit, which typically monitors coolant temperature at the radiator outlet or a second point in the cooling system. The PCM expects a voltage within a calibrated range, and a sustained low reading indicates a short to ground, an open return, or a sensor that is pulling the signal low.

P2184 means the powertrain control module (PCM) has detected a low-voltage signal on the Engine Coolant Temperature Sensor 2 circuit, which typically monitors coolant temperature at the radiator outlet or a second point in the cooling system. The PCM expects a voltage within a calibrated range, and a sustained low reading indicates a short to ground, an open return, or a sensor that is pulling the signal low.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Cooling fan running continuously or at high speed because the PCM sees an implausibly cold or faulty reading
Poor fuel economy or rich-running condition if the PCM substitutes a default coolant temperature
Inaccurate or erratic temperature gauge reading on the dashboard
Possible overheating in traffic if the fan strategy is disabled by the fault
Hard starting or rough idle when cold if the PCM cannot trust the second coolant sensor

Common causes, most likely first

Faulty Engine Coolant Temperature Sensor 2 internally shorted to ground
Damaged or chafed sensor wiring shorted to ground between the sensor and the PCM
Corroded, loose, or pushed-back terminal at the sensor connector or PCM connector
Open ground return circuit for the sensor, causing the PCM to read a low signal
Coolant intrusion into the sensor connector or sensor body
PCM internal fault pulling the sensor signal low (rare)

How to diagnose and fix it

Scan all modules and record freeze-frame data for P2184 to confirm the fault conditions and check for related codes
Inspect the ECT Sensor 2 connector and wiring for corrosion, chafing, or coolant intrusion, and repair as needed
Measure sensor resistance with a multimeter and compare to the manufacturer's temperature-resistance chart
Back-probe the sensor signal circuit at the PCM and check voltage with the key on, engine off, looking for a value near 0 volts
Disconnect the sensor and check for a short to ground on the signal wire; repair the harness if a short is found
Verify the sensor ground circuit has less than 0.1 volts drop under load; repair the ground if excessive
Replace the ECT Sensor 2 only after electrical testing confirms the sensor is the cause, then clear codes and verify the repair

Second coolant sensor faults that fool technicians

A low signal code often comes from a chafed wire grounding against the engine block rather than a failed sensor, so a visual harness inspection is more valuable than parts swapping.
Some vehicles use ECT Sensor 2 primarily for radiator outlet temperature and fan control, so a fault can cause the cooling fan to run constantly even when the engine temperature gauge looks normal.
A corroded connector pin can add resistance that mimics a short to ground, and simply unplugging and reconnecting the sensor may temporarily clear the code without fixing the root cause.
P2184 can be set by a poor engine ground strap that raises the reference voltage on the sensor return circuit, so checking chassis grounds is part of a thorough diagnosis.
Do not assume the sensor is bad because the code says low; a shorted signal wire will read low with the sensor disconnected, which is the quickest way to separate a sensor fault from a harness fault.

Can I keep driving with P2184?

You can usually drive with P2184, but avoid heavy traffic and long idling because the cooling fan may not operate correctly and the engine could overheat. If the temperature gauge climbs above normal or you see steam, stop safely and shut the engine off.

Tools that help

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