Technical Description of OBD-II Trouble Code
The circuit for Engine Coolant Temperature (ECT) Sensor #2 is experiencing a low input.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to all vehicles manufactured in 1996 or later (Honda, Toyota, Volkswagen VW, Mazda, Dodge, Ford, BW, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The ECT (Engine coolant temperature) sensor is a thermistor located in the engine block or another coolant passage. It changes resistance as the temperature of the coolant it is in contact with changes. Typically, it is a two-wire sensor, with one wire receiving a 5-volt reference from the PCM (Powertrain Control Module) and the other wire serving as the ground supplied from the PCM.
As the coolant temperature changes, the resistance of the sensor also changes. When the engine is cold, the resistance is high, and when the engine is warm, the resistance is low. If the PCM detects a signal voltage lower than the normal operating range of the sensor, the P2184 code will be set.
An example of an Engine Coolant Temperature ECT sensor
Note: This DTC is essentially identical to P0117, but the difference with this code is that it refers to the #2 ECT sensor circuit. Therefore, vehicles displaying this code have two ECT sensors. Make sure you are diagnosing the correct sensor circuit.
Symptoms
Potential symptoms include:
Causes
Potential causes of the P2184 code include:
Possible Solutions
Since this code indicates an abnormally low signal to the PCM from the #2 ECT sensor, the PCM has detected an excessively “hot” condition in the engine coolant. This could be due to a faulty ECT sensor or wiring, but it could also be caused by an overheated engine. Therefore, if your engine has overheated, diagnose that issue first. With that said, here are the possible solutions:
Using a scan tool, check the #2 ECT sensor reading on the display with the KOEO (Key on engine off). On a cold engine, the ECT reading should match the IAT (Intake Air Temperature) sensor reading. If it does not, replace the #2 ECT sensor.
1. If the ECT reading shows an excessively hot reading, such as more than 260 deg. F, unplug the ECT sensor. This should cause the ECT reading to drop to the extreme cold reading (around -30 deg.F or so). If it does, replace the sensor because it is internally shorted. If the reading does not change, check for a short to ground on the signal circuit of the ECT wiring. It is possible that the two ECT wires are shorted to each other. Look for any chafing or melted wiring and repair as necessary.
a. If you cannot find any wiring problems and the ECT reading does not drop to the extreme coldest when unplugged, check for voltage coming out of the PCM on the signal wire’s pin at the PCM connector. If there is no voltage or it is low, the PCM may be faulty. NOTE: On some models, the 5 Volt reference signal can be temporarily shorted. This can occur if an engine sensor internally shorts the 5 Volt reference. Since the 5 Volt reference is a “shared” circuit on many models, this will cause it to be abnormally low. Usually, this will be accompanied by several other sensor codes. If you suspect this may be the case, unplug each sensor until the 5 Volt reference reappears. The last sensor unplugged is the offending sensor. Replace it and recheck the signal wire from the PCM connector.
2. If the scan tool ECT reading appears normal at this time, the problem may be intermittent. Use a “wiggle” test to manipulate the wiring harness and connectors while observing the ECT reading on the scan tool. Repair any loose or corroded wiring or connectors. If your scan tool has the Freeze frame data function, you can check the ECT reading when the failure occurred. If it shows the reading to be at the hottest extreme, replace the ECT sensor and see if the code reappears.
Related ECT sensor circuit codes: P0115, P0116, P0117, P0118, P0119, P0125, P0128, P2182, P2183, P2185, P2186
