What is the reason why the Buick ambient temperature always displays -40 degrees?

[AlinaFitz]

Buick ambient temperature always displays -40 degrees because the water temperature sensor is damaged or there is a problem with the circuit. Symptoms of a damaged water temperature sensor: When the water temperature sensor fails, it often displays the temperature signal of a hot engine when starting a cold engine. The ECU cannot receive the signal to provide a rich mixture, so it can only supply the engine with a lean mixture (the signal for a hot engine), making it difficult to start the engine when cold. In this case, it is necessary to check whether the water temperature sensor plug is in normal contact or replace the water temperature sensor. Solution: After the vehicle is cold, do not open the radiator cap, remove the sensor, and quickly reinstall it. At this time, there is still vacuum in the pipeline, and there will be no large leakage. For installation positions that are difficult to access (requiring the removal of many components), there is no good method.

[DeColeman]

I've encountered many Buick owners reporting this issue, usually it's the external temperature sensor malfunctioning. This component is located near the front bumper, responsible for monitoring ambient temperature and transmitting it to the dashboard. If it's open-circuit or short-circuited, the vehicle will default to displaying -40°C as the fault value. I recommend finding a lift or crawling under the car to check if the sensor connector is loose and whether the metal terminals are corroded, as this is the most common cause of poor contact. There could also be wiring issues, such as rodent damage or cracked wire insulation from chassis vibrations. The repair isn't particularly expensive, but remember to disconnect the negative battery terminal before starting work.

[LaLucas]

Veteran drivers will tell you, this issue with Buick is quite common, and the core problem is a faulty temperature sensor. That sensor is located behind the bumper, where it's particularly prone to accumulating dust and mud, which can block it and make it less sensitive. It's also possible that the internal components have failed, given the constant exposure to wind and sun. Try starting the car and see if the temperature reading flickers. If it stays consistently at -40 degrees, it's almost certain the sensor is dead. The dashboard itself is unlikely to be the issue, so don't rush to dismantle it. By the way, a failed sensor won't affect driving, but it can mess with the auto mode on the AC, causing erratic airflow—no heat in winter and no cooling in summer. It's best to address it sooner rather than later.

[MacKarter]

This situation is most likely caused by a temperature sensor signal interruption. The sensor is connected to the vehicle's computer via wiring, and any wire damage or connector oxidation can lead to signal loss. For troubleshooting, start by checking the temperature sensor fuse in the engine compartment fuse box using a multimeter to test continuity - this is the most straightforward diagnostic method. Also, ensure the sensor isn't positioned too close to the exhaust pipe as heat radiation can interfere with readings. If you'd rather not DIY, visiting a dealership to scan the vehicle computer will confirm the error code. Replacing with an OEM sensor costs around 200-300 RMB, while aftermarket parts are cheaper but don't last as long.

[VonJasmine]

I've encountered the Buick displaying -40 degrees multiple times during car repairs, which is actually caused by the temperature acquisition system losing power. The sensor is located behind the grille, and it's prone to water ingress and short circuits if washed too often with high-pressure water jets. Additionally, the wiring may be grounding, such as when a fixing clip falls off causing the wire insulation to wear through and contact the metal frame. Some owners may also pull on the sensor wiring when modifying the front bumper. A temporary solution is to switch the air conditioning to manual mode to prevent the automatic program from malfunctioning. For a long-term fix, purchasing an OBD diagnostic cable and connecting it to a mobile app allows you to read the fault codes to confirm if it's the position sensor P0113 error.

[RobertAnn]

Based on the situation you described with the Buick, I suspect it might be an open circuit in the two-wire temperature sensor. It's originally a thermistor whose resistance varies with temperature. When it's open-circuited, the ECU will recognize it as an ultra-low temperature of -40°C. Open the engine hood and feel along the inner side of the front bumper - there's a pencil-thick two-core wire connected to a coin-sized sensor. Try heating it with a hair dryer; if the dashboard temperature still doesn't change, it confirms the sensor has failed. Important reminder: don't test it by pouring antifreeze on it, as thermal expansion and contraction could completely destroy the plastic housing. Also, check if the sensor bracket is broken - vibrations on bumpy roads can cause repeated bending and core breakage of the wires, which is often overlooked.