What are the symptoms of the temperature sensor on a Ford Transit Custom?

The temperature sensor in a Ford Transit Custom is a critical component that monitors the engine's temperature and relays this information to the vehicle's computer. If the temperature sensor is malfunctioning, it can cause a range of issues that can impact the vehicle's performance and overall health. In this article, we'll explore the common symptoms associated with a faulty temperature sensor in a Ford Transit Custom.

Overheating Engine

One of the most obvious symptoms of a faulty temperature sensor is an overheating engine. If the sensor is not accurately reporting the engine's temperature, the computer may not be able to properly regulate the cooling system, leading to the engine overheating. This can result in the temperature gauge on the dashboard reading higher than normal, or the engine coolant temperature warning light illuminating.

Erratic Temperature Readings

Another common symptom of a malfunctioning temperature sensor is erratic or fluctuating temperature readings on the dashboard. The temperature gauge may bounce around or show inconsistent readings, indicating that the sensor is not providing accurate information to the vehicle's computer.

Poor Fuel Economy

A faulty temperature sensor can also impact the vehicle's fuel efficiency. If the computer is not receiving accurate temperature data, it may adjust the fuel-air mixture incorrectly, leading to increased fuel consumption and reduced gas mileage.

Difficulty Starting the Engine

In some cases, a malfunctioning temperature sensor can make it difficult to start the engine, especially when the engine is cold. The computer may not be able to properly adjust the fuel-air mixture, making it harder for the engine to start and run smoothly.

Illuminated Check Engine Light

If the temperature sensor is not functioning correctly, the vehicle's on-board diagnostics system may detect the issue and illuminate the check engine light on the dashboard. This is the computer's way of alerting the driver to a problem that needs to be addressed.p>

In summary, the primary symptoms of a faulty temperature sensor in a Ford Transit Custom include overheating, erratic temperature readings, poor fuel economy, difficulty starting the engine, and an illuminated check engine light. If you experience any of these issues, it's important to have the vehicle inspected by a qualified mechanic to diagnose and address the problem.

How do I know if my temperature sensor is bad?

You can tell your temperature sensor is bad by noticing common symptoms like an illuminated check engine light, the engine overheating or running cold, poor fuel efficiency, or an erratic temperature gauge that fluctuates wildly or shows inaccurate readings. Other signs include rough idling, engine misfires, or difficulty starting the car.
 
This video explains the symptoms of a bad engine coolant temperature sensor: 1mMechanic BaseYouTube · Feb 6, 2024
Common symptoms

• Check engine light: The check engine light often turns on when the car's computer detects a fault with the sensor. 
• Engine overheating or running cold: A faulty sensor can prevent the engine from reaching its optimal operating temperature, causing it to overheat or, conversely, to run inefficiently cold. 
• Erratic temperature gauge: The gauge on your dashboard may show inaccurate readings, such as rapidly fluctuating, staying stuck at one reading, or showing extreme high or low temperatures. 
• Poor fuel economy: If the sensor sends a faulty "cold" signal, the engine control unit (ECU) may inject more fuel than necessary, leading to worse gas mileage. 
• Rough idling and engine misfires: The sensor's data is used to calculate the air-fuel mixture. Incorrect data can cause the engine to idle roughly, misfire, or stall. 
• Difficulty starting: A bad sensor can make it hard to start the car, particularly if it's warm, as the ECU might be injecting too much or too little fuel. 
• Cooling fan issues: A failing sensor may not correctly signal the cooling fans to turn on when needed, leading to overheating. 
• Black smoke from exhaust: An incorrect reading can lead to a rich fuel mixture (too much fuel), causing black smoke to come from the exhaust. 

You can watch this video to learn about the symptoms of a bad coolant temperature sensor: 59sCar Computer ExchangeYouTube · Jun 6, 2023
How to diagnose further

• Use a scan tool: A diagnostic scan tool can read trouble codes from the ECU that specifically point to a bad temperature sensor, such as P0115 or P2185. 
• Test with a multimeter: For a more hands-on test, you can use a multimeter to check the sensor's resistance and compare it to the manufacturer's specifications. 

Can a temperature sensor affect engine starting?

Yes, a malfunctioning temperature sensor can affect engine starting, most commonly by causing a hard start or a "no start" situation, especially in cold weather. A faulty coolant temperature sensor, for instance, can send incorrect information to the engine's computer (ECU), causing it to fail to deliver the correct air-fuel mixture for a proper start. 
This video explains how a faulty engine coolant temperature sensor can lead to hard starting: 58sproclaimliberty2000YouTube · Jul 21, 2019
How a faulty temperature sensor affects starting

• Incorrect fuel mixture: During a cold start, the engine needs a rich mixture of fuel and air to start. If the sensor incorrectly signals that the engine is warm, the ECU will inject too little fuel, leading to difficult starting or a failure to start at all. 
• No start condition: A failing sensor can sometimes send a signal that is so far off that the engine simply won't start. 
• Other symptoms: In addition to starting issues, a bad temperature sensor can cause other problems like poor fuel economy, rough idling, and the check engine light to illuminate. 

This video demonstrates various signs of a bad engine coolant temperature sensor, including hard starting: 58sHonest Mechanic ColoradoYouTube · Oct 31, 2023

What are signs of a bad transmission temperature sensor?

Symptoms of a bad transmission temperature sensor include warning lights on the dashboard, harsh or delayed gear shifts, and the vehicle entering "limp mode". Other signs can be a burning smell from overheating transmission fluid, poor fuel economy, and erratic torque converter operation.
 
Performance and shifting issues 

• Delayed or harsh shifting: The transmission may hesitate before shifting or shift abruptly. 
• Limp mode: The vehicle may enter a low-power mode to prevent damage, resulting in limited speed and inability to change gears. 
• Torque converter problems: The torque converter clutch may not engage or disengage properly, leading to shuddering, especially at highway speeds. 

Warning signs

• Dashboard lights: A transmission temperature warning light, check engine light, or other related warning lights may illuminate. 
• Burning smell: An odor of burning can indicate the transmission fluid is overheating. 
• Poor fuel economy: If the torque converter doesn't lock up, it can lead to decreased gas mileage. 

Other symptoms

• Difficulty starting: In some cases, a faulty sensor can prevent the car from starting. 
• Hesitation: The car may hesitate or feel sluggish when accelerating. 
• Transmission fluid overheating: While this is a cause for concern, it's often the sensor's fault that the temperature is not accurately reported, leading to the other symptoms. 

What happens if I unplug the coolant temperature sensor on my Ford?

It's not recommended to unplug the coolant temperature sensor unless necessary for diagnostic purposes, as it can adversely affect engine operation and potentially cause damage if left unplugged for an extended period.