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P2185 OBD-II Trouble Code: Engine Coolant Temperature Sensor 2 Circuit High

Check Engine Light

P2185 code definition

Engine Coolant Temperature Sensor 2 Circuit High

What the P2185 code means

This code indicates that the sensor is sending data to the PCM (Powertrain Control Module) indicating a cooler coolant temperature that may actually exist.

What causes the P2185 code?

This ECT (Engine Coolant Temperature) is one of two sensors the PCM uses to monitor the operating temperature of the engine. The PCM compares the voltage readings of sensor 1, sensor 2, and how long the motor has been running. If the motor has been running for a time, the PCM concludes the coolant should be warmer than ambient temperature and uses this reasoning to determine which sensor is reading incorrectly and sets a code accordingly.

What are the symptoms of the P2185 code?

Usually a Check Engine Light is the only symptom that is observed. If the PCM concludes that the vehicle is operating at a temperature it is not, this could lead to a very rich or very lean air-fuel mixture because the PCM doesn’t have an accurate voltage reading.

How does a mechanic diagnose the P2185 code?

Connecting a scan tool and reading the scan tool data usually results in a quick diagnosis. The technician can simply compare the temperature reading of sensor 2 and compare this to the what the technician knows to be true. If the car is cold, the sensor should show how much and vice versa. In some cases, the sensor can just be out of specification with what the PCM expects to see. In this case, it will be necessary for the technician to remove the sensor and bench test it.

Bench testing of this type of sensor requires a multimeter that can be set to ohms and something to heat the sensor up with. Usually a small butane torch will do the trick. The multimeter is used to measure the sensor resistance while the torch is used to gently warm the sensor. There should be a proportionate change in resistance as the sensor is warmed. Depending on the manufacturer, each sensor will have a different temperature to resistance curve. This information will be supplied by the manufacturer.

Common mistakes when diagnosing the P2185 code

Failing to check the coolant level is easy to forget. A low coolant level can lead to many unpredictable symptoms and codes. The coolant level must be full, and the thermostat must be operating correctly before this code can be accurately diagnosed. The cooling system is the system that keep your engine from overheating.

With two sensors, it can be confusing as to which sensor is sensor 1 and which one is sensor 2. At times, we make the mistake of replacing the wrong sensor. Determining which sensor is sensor 1 is not always as simple as it seems. Some manufacturers information is better than others. If a mechanic is unable to be sure which sensor is which, depending on their cost and difficulty to replace, it may be prudent to replace them both.

Often times, the problem isn’t the sensor itself but the connector or wiring to the sensor. Time should be taken to inspect the connector and the related harness. If the sensor bench tests good, it may be necessary check for continuity (testing a wire for high resistance) through the harness to the PCM.

How serious is the P2185 code?

This code usually is not problematic, as this code will only be used by manufacturers who choose to utilize two or more ECT sensors. This redundancy allows the manufacturer the ability to more effectively calculate air-fuel mixture under varying conditions, as well as redundancy if one sensor should fail. This is significant because the coolant temperature sensor is the primary sensor the PCM uses to decide what operational mode to be used. Whether it be a cold start up condition or fine tuning of the air-fuel mixture.

Depending on the programming the manufacturer chooses to use, if the sensor that this code represents fails, the vehicle may not start. If you do manage to get it to run, it will run excessively rich with black smoke out of the tailpipe.

What repairs can fix the P2185 code?

Additional comments for consideration regarding the P2185 code

This code has the potential to render a vehicle undrivable, but mostly likely will only result in a Check Engine Light. What results depends on the manufacturer's choice of programming and the exact failure of the sensor.

A complete failure will often yield drivability symptoms, but will most often lead to the sensor being a little out of specification from what the computer is expecting to see. Often times this prompts the manufacturer to reflash the PROM (Program Read Only Memory) in the PCM. This is similar to an update you would perform to your home PC.

Need help with a P2185 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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