What happens when the oil temperature sensor fails?
4 Answers
When the oil temperature sensor fails, it may result in automatic gear disengagement, gear misalignment, wear patterns of major transmission components, and their impact on the overall assembly performance. Below are the relevant details: Working principle: In automotive terms, a temperature sensor is a device that measures temperature, providing signals to the instrument panel for engine coolant temperature, to the cooling fan, and to the ECU for fuel injection correction. Working principle: The coolant temperature sensor is a negative temperature coefficient thermistor, where resistance decreases as temperature rises, and vice versa, providing the ECU with a variable signal. Classification: It utilizes the regular changes in various physical properties of materials with temperature to convert temperature into electrical signals. These regularly changing physical properties mainly include volume. Temperature sensors are the core components of temperature measurement instruments, with a wide variety available. They can be divided into contact and non-contact types based on measurement methods, and into thermistors and thermocouples based on sensor materials and electronic component characteristics.
This issue is indeed quite a headache. I've experienced it myself with my old manual transmission car. When the oil temperature sensor fails, the temperature needle on the dashboard just freezes completely, which is especially nerve-wracking on highways. The transmission oil over-temperature protection function stops working entirely. Once, when starting on a slope, I clearly felt severe gearshift hesitation, as if there was sand stuck in the gears. It gets worse in summer - you'd suddenly smell burning engine oil while driving, and later found out it was caused by uncontrolled temperature leading to oil evaporation. The mechanic said the sensor is awkwardly located near the transmission oil pan, requiring removal of the engine guard plate for access, which took a whole half day to fix.
As a commuter who drives 60 kilometers daily, I dread encountering such electronic malfunctions in my car. Initially, the faulty oil temperature sensor only caused erratic readings on the dashboard, but later it went completely black. Once, during a half-hour traffic jam, the transmission suddenly locked in 3rd gear, and no matter how hard I pressed the accelerator, the car wouldn't speed up. The mechanic used a diagnostic tool to retrieve the P0711 trouble code, explaining that the transmission computer had defaulted to overheating protection mode, assuming an oil temperature of 128°C. Even more annoying is the sluggish transmission response during cold starts, like a person moving in slow motion during winter. Now, I've developed a habit of scanning the car's computer with an OBD scanner every six months.
To be honest, a faulty sensor is much more troublesome than imagined. During last year's road trip, the oil temperature display on the dashboard suddenly dropped to zero, and I didn't pay attention at the time. The next day while climbing mountain roads, the transmission started jerking noticeably like riding a horse, and during downhill driving, the transmission overheated and went into protective lockout mode. After towing it to the repair shop, we found that the sensor connector had been short-circuited by mud splashed from the chassis. The mechanic said this could cause the transmission control module to misjudge conditions - for example, applying hot-engine logic when cold-start oil pressure should be increased, resulting in doubled belt slippage and wear. Now whenever I see abnormal oil temperature readings, I stop immediately to check, terrified of facing a major transmission overhaul.
