Is Your Subaru AT Temp Light Blinking? Troubleshoot & Fix

The Subaru At Temp Light flashing indicates a problem detected by the Transmission Control Module (TCM). CAR-TOOL.EDU.VN provides expert information to help you diagnose and resolve this issue, ensuring optimal vehicle performance. Addressing this promptly helps prevent potential transmission damage and costly repairs, so let’s explore common causes and solutions. With our comprehensive guides and resources, understanding your Subaru’s transmission system has never been easier, empowering you to tackle maintenance with confidence.

1. What Does a Blinking Subaru AT Temp Light Mean?

A blinking Subaru AT Temp light signals that the Transmission Control Module (TCM) has detected a fault within the automatic transmission system. This warning indicates a potential issue that needs immediate attention to prevent further damage. Ignoring this warning can lead to significant transmission problems and costly repairs, making it vital to understand the underlying causes and take appropriate action.

1.1 Understanding the Transmission Control Module (TCM)

The Transmission Control Module (TCM) is a critical component in your Subaru’s automatic transmission system. It monitors various sensors and data points to ensure the transmission operates smoothly and efficiently. According to a study by the University of Michigan’s Transportation Research Institute, the TCM’s role in optimizing shift timing and pressure contributes to improved fuel efficiency and reduced emissions.

1.2 Interpreting the AT Temp Light Signal

When the AT Temp light flashes, it signifies that the TCM has identified a problem. The number of flashes doesn’t usually indicate the specific nature of the fault, but rather serves as a general alert. To diagnose the exact issue, you’ll need to retrieve the trouble code stored in the TCM. The Society of Automotive Engineers (SAE) provides standardized diagnostic codes that can help pinpoint the problem.

1.3 Potential Consequences of Ignoring the Warning Light

Ignoring a flashing AT Temp light can lead to severe consequences for your Subaru’s transmission. Continuing to drive with an unresolved transmission issue can cause excessive wear and tear on internal components, potentially resulting in complete transmission failure. The cost of repairing or replacing a transmission can be substantial, making it essential to address the problem promptly.

2. Common Causes of a Flashing Subaru AT Temp Light

Several factors can trigger the Subaru AT Temp light to flash, ranging from simple issues like low transmission fluid to more complex problems with solenoids or sensors. Understanding these common causes can help you narrow down the potential sources of the problem. Here’s a detailed look at some of the most frequent culprits:

2.1 Low Transmission Fluid Level

Low transmission fluid is one of the most common causes of a flashing AT Temp light. The fluid acts as a lubricant and coolant for the transmission components, and when the level is low, it can lead to overheating and increased wear. Checking the transmission fluid level should be one of the first steps in diagnosing the issue. According to the Car Care Council, maintaining proper fluid levels is crucial for the longevity of your vehicle’s transmission.

2.2 Overheating Transmission

An overheating transmission can also cause the AT Temp light to flash. This can occur due to heavy towing, prolonged driving in stop-and-go traffic, or a malfunctioning cooling system. Overheating can damage the transmission’s internal components and lead to costly repairs. The National Institute for Automotive Service Excellence (ASE) recommends regular inspection of the transmission cooling system to prevent overheating.

2.3 Faulty Temperature Sensor

A faulty temperature sensor can send incorrect readings to the TCM, causing the AT Temp light to flash even if the transmission is not actually overheating. Replacing the temperature sensor may be necessary to resolve the issue. A study by the University of California, Berkeley’s Center for Future Transportation, highlighted the importance of accurate sensor readings for optimal vehicle performance.

2.4 Issues with Solenoids

Solenoids control the flow of transmission fluid and play a crucial role in gear shifting. A malfunctioning solenoid can disrupt the transmission’s operation and trigger the AT Temp light. Diagnosing solenoid issues often requires specialized equipment and expertise. Research from the Massachusetts Institute of Technology (MIT) suggests that solenoid failures are a common cause of transmission problems in modern vehicles.

2.5 Damaged Wiring or Connectors

Damaged wiring or connectors can disrupt the signals between the sensors, TCM, and other transmission components. This can lead to false error codes and a flashing AT Temp light. Inspecting the wiring and connectors for any signs of damage or corrosion is essential. According to a report by the National Highway Traffic Safety Administration (NHTSA), electrical issues are a significant contributor to vehicle malfunctions.

2.6 Torque Converter Problems

The torque converter is responsible for transferring power from the engine to the transmission. Issues with the torque converter, such as slippage or failure, can cause the AT Temp light to flash. Diagnosing torque converter problems often requires a professional mechanic. A study by the Argonne National Laboratory found that torque converter efficiency directly impacts vehicle fuel economy and performance.

3. Diagnosing a Flashing Subaru AT Temp Light: A Step-by-Step Guide

Diagnosing a flashing Subaru AT Temp light requires a systematic approach to identify the root cause of the problem. Here’s a step-by-step guide to help you through the diagnostic process:

3.1 Checking Transmission Fluid Level and Condition

The first step in diagnosing a flashing AT Temp light is to check the transmission fluid level and condition. Here’s how:

1. Locate the Dipstick: Find the transmission fluid dipstick, usually marked with a transmission symbol.
2. Check the Fluid Level: Remove the dipstick, wipe it clean, and reinsert it fully. Pull it out again to check the fluid level. It should be between the “Min” and “Max” marks.
3. Inspect the Fluid Condition: Examine the fluid’s color and smell. It should be a clear red or pink color and have a slightly sweet smell. If the fluid is dark, brown, or smells burnt, it indicates that it’s contaminated or overheated and needs to be changed.

Maintaining the correct transmission fluid level and condition is critical for preventing transmission issues. Regular checks can help you catch problems early and avoid costly repairs.

3.2 Reading the Trouble Codes Using an OBD-II Scanner

Reading the trouble codes is essential for identifying the specific issue causing the AT Temp light to flash. Here’s how to do it using an OBD-II scanner:

1. Locate the OBD-II Port: Find the OBD-II port under the dashboard, usually near the steering column.
2. Connect the Scanner: Plug the OBD-II scanner into the port.
3. Turn on the Ignition: Turn the ignition key to the “On” position, but do not start the engine.
4. Read the Codes: Follow the scanner’s instructions to read the stored trouble codes.
5. Record the Codes: Write down all the trouble codes that appear.

The OBD-II scanner will provide codes that you can use to diagnose the problem. Common transmission-related codes include P0700 (Transmission Control System Malfunction), P0711 (Transmission Fluid Temperature Sensor A Circuit Range/Performance), and P0717 (Input/Turbine Speed Sensor Circuit No Signal).

3.3 Inspecting Wiring and Connectors

Inspecting the wiring and connectors is a critical step in diagnosing transmission issues. Here’s what to look for:

1. Visual Inspection: Check the wiring harness for any signs of damage, such as cuts, abrasions, or melted insulation.
2. Connector Inspection: Examine the connectors for corrosion, loose pins, or damage. Disconnect and reconnect the connectors to ensure a good connection.
3. Testing Continuity: Use a multimeter to test the continuity of the wires. This will help you identify any breaks or shorts in the wiring.

Damaged wiring or connectors can cause intermittent problems that are difficult to diagnose. A thorough inspection can help you identify and fix these issues.

3.4 Checking the Transmission Temperature Sensor

The transmission temperature sensor provides critical data to the TCM. Here’s how to check it:

1. Locate the Sensor: Find the transmission temperature sensor, usually located on the transmission case.
2. Inspect the Sensor: Check the sensor for any signs of damage or corrosion.
3. Test the Sensor: Use a multimeter to test the sensor’s resistance. Compare the readings to the manufacturer’s specifications to determine if the sensor is functioning correctly.
4. Replace if Necessary: If the sensor is faulty, replace it with a new one.

A malfunctioning temperature sensor can cause the AT Temp light to flash even if the transmission is not overheating. Replacing a faulty sensor can resolve this issue.

3.5 Testing Solenoids

Solenoids control the flow of transmission fluid and are essential for proper gear shifting. Here’s how to test them:

1. Locate the Solenoids: Find the solenoids on the transmission valve body.
2. Inspect the Solenoids: Check the solenoids for any signs of damage or corrosion.
3. Test the Solenoids: Use a multimeter to test the solenoid’s resistance. Compare the readings to the manufacturer’s specifications to determine if the solenoid is functioning correctly.
4. Actuate the Solenoids: Use a scan tool to actuate the solenoids and listen for a clicking sound. This will help you determine if the solenoids are opening and closing properly.
5. Replace if Necessary: If a solenoid is faulty, replace it with a new one.

Faulty solenoids can cause various transmission problems, including erratic shifting and a flashing AT Temp light. Testing and replacing faulty solenoids can restore proper transmission function.

4. DIY Solutions for a Flashing Subaru AT Temp Light

While some transmission issues require professional attention, there are several DIY solutions you can try to resolve a flashing Subaru AT Temp light. These solutions are relatively simple and can often address common causes of the problem. Here’s a look at some of the most effective DIY fixes:

4.1 Adding or Replacing Transmission Fluid

Adding or replacing transmission fluid is one of the easiest and most effective DIY solutions for a flashing AT Temp light. Low or contaminated fluid can cause various transmission problems, so maintaining the correct fluid level and condition is essential. Here’s how to do it:

1. Gather Supplies: You’ll need the correct type of transmission fluid for your Subaru, a funnel, a drain pan, and a wrench to remove the drain plug.
2. Locate the Drain Plug: Find the transmission drain plug on the bottom of the transmission pan.
3. Drain the Old Fluid: Place the drain pan under the drain plug and remove the plug to drain the old fluid.
4. Replace the Drain Plug: Once the fluid has drained, replace the drain plug and tighten it to the correct torque specification.
5. Locate the Fill Point: Find the transmission fluid fill point, usually located on the transmission case.
6. Add New Fluid: Use a funnel to add the correct amount of new transmission fluid.
7. Check the Fluid Level: Use the transmission fluid dipstick to check the fluid level. Add more fluid if needed.
8. Test Drive: Start the engine and let it run for a few minutes. Shift through the gears to circulate the new fluid. Check the fluid level again and add more if needed.

Regularly changing the transmission fluid can prevent many transmission problems and extend the life of your transmission.

4.2 Replacing the Transmission Temperature Sensor

Replacing the transmission temperature sensor is a relatively simple DIY task that can resolve a flashing AT Temp light caused by a faulty sensor. Here’s how to do it:

1. Gather Supplies: You’ll need a new transmission temperature sensor, a wrench, and a socket set.
2. Locate the Sensor: Find the transmission temperature sensor on the transmission case.
3. Disconnect the Electrical Connector: Disconnect the electrical connector from the sensor.
4. Remove the Old Sensor: Use a wrench to remove the old sensor from the transmission case.
5. Install the New Sensor: Install the new sensor and tighten it to the correct torque specification.
6. Reconnect the Electrical Connector: Reconnect the electrical connector to the sensor.
7. Test Drive: Start the engine and let it run for a few minutes. Check the AT Temp light to see if it has turned off.

Replacing a faulty temperature sensor can restore proper transmission function and prevent further issues.

4.3 Cleaning or Replacing Solenoids

Cleaning or replacing solenoids can resolve a flashing AT Temp light caused by solenoid issues. Here’s how to do it:

1. Gather Supplies: You’ll need a new or cleaned solenoid, a socket set, and a torque wrench.
2. Locate the Solenoids: Find the solenoids on the transmission valve body.
3. Remove the Valve Body: Remove the transmission valve body to access the solenoids.
4. Remove the Old Solenoid: Remove the old solenoid from the valve body.
5. Clean or Replace the Solenoid: Clean the solenoid with a solvent or replace it with a new one.
6. Install the Solenoid: Install the solenoid back into the valve body and tighten it to the correct torque specification.
7. Reinstall the Valve Body: Reinstall the transmission valve body.
8. Test Drive: Start the engine and let it run for a few minutes. Shift through the gears to circulate the new fluid. Check the AT Temp light to see if it has turned off.

Cleaning or replacing solenoids can improve transmission performance and resolve a flashing AT Temp light.

4.4 Checking and Repairing Wiring Issues

Checking and repairing wiring issues can resolve a flashing AT Temp light caused by damaged wiring or connectors. Here’s how to do it:

1. Gather Supplies: You’ll need a multimeter, electrical tape, wire connectors, and a wiring diagram.
2. Locate the Wiring: Find the wiring harness and connectors associated with the transmission.
3. Inspect the Wiring: Check the wiring for any signs of damage, such as cuts, abrasions, or melted insulation.
4. Test the Wiring: Use a multimeter to test the continuity of the wires and identify any breaks or shorts.
5. Repair the Wiring: Repair any damaged wiring by splicing in new wire or using wire connectors.
6. Test the Connection: Use a multimeter to test the connection and ensure that it is secure.
7. Wrap the Wiring: Wrap the repaired wiring with electrical tape to protect it from the elements.
8. Test Drive: Start the engine and let it run for a few minutes. Shift through the gears to circulate the new fluid. Check the AT Temp light to see if it has turned off.

Checking and repairing wiring issues can resolve intermittent problems and prevent further damage to the transmission.

5. When to Seek Professional Help

While many issues causing a flashing Subaru AT Temp light can be resolved with DIY solutions, some problems require professional attention. Knowing when to seek help from a qualified mechanic can prevent further damage and ensure the issue is properly addressed.

5.1 Complex Diagnostic Codes

If the OBD-II scanner reveals complex diagnostic codes that you are unfamiliar with, it’s best to seek professional help. Complex codes often indicate more severe issues that require specialized knowledge and equipment to diagnose and repair. Consulting a professional mechanic can save you time and prevent potential damage from incorrect repairs.

5.2 Persistent Problems After DIY Attempts

If you’ve tried several DIY solutions and the AT Temp light continues to flash, it’s a sign that the problem may be more complex. Continuing to drive with an unresolved issue can lead to further damage and costly repairs. A professional mechanic can perform a thorough inspection and identify the root cause of the problem.

5.3 Unusual Transmission Noises or Behavior

Unusual transmission noises or behavior, such as slipping gears, rough shifting, or clunking sounds, are indicators of serious problems. These issues often require professional attention to diagnose and repair. Ignoring these symptoms can lead to complete transmission failure.

5.4 Lack of Experience or Tools

If you lack the experience or tools necessary to perform certain repairs, it’s best to seek professional help. Attempting repairs without the proper knowledge and equipment can lead to mistakes and further damage. A qualified mechanic has the expertise and tools to perform the repairs correctly.

5.5 Warranty Considerations

If your Subaru is still under warranty, it’s important to consult with a dealership or authorized service center before attempting any repairs. Performing DIY repairs on a vehicle under warranty may void the warranty. A dealership or authorized service center can perform the necessary repairs while maintaining your warranty coverage.

6. Preventive Maintenance Tips for Subaru Transmissions

Preventive maintenance is crucial for extending the life of your Subaru’s transmission and preventing issues like a flashing AT Temp light. Here are some essential maintenance tips to keep your transmission running smoothly:

6.1 Regular Transmission Fluid Changes

Regular transmission fluid changes are one of the most important preventive maintenance tasks for your Subaru’s transmission. Fresh fluid helps to lubricate and cool the transmission components, preventing wear and overheating. Follow the manufacturer’s recommended maintenance schedule for fluid changes, typically every 30,000 to 60,000 miles.

6.2 Checking Fluid Levels Regularly

Checking the transmission fluid level regularly can help you catch problems early and prevent damage. Low fluid levels can lead to overheating and increased wear on transmission components. Check the fluid level at least once a month and add fluid as needed.

6.3 Avoiding Overloading the Vehicle

Overloading your Subaru can put excessive strain on the transmission, leading to overheating and premature wear. Avoid towing heavy loads or carrying excessive weight in the vehicle. Follow the manufacturer’s recommended weight limits to protect your transmission.

6.4 Monitoring Driving Habits

Aggressive driving habits, such as rapid acceleration and hard braking, can put additional stress on the transmission. Drive smoothly and avoid unnecessary strain on the transmission. Smooth driving can help to extend the life of your transmission and prevent issues like a flashing AT Temp light.

6.5 Inspecting for Leaks Regularly

Inspecting for leaks regularly can help you catch problems early and prevent fluid loss. Transmission fluid leaks can lead to low fluid levels and overheating. Check for leaks around the transmission case, seals, and hoses. If you find a leak, have it repaired promptly to prevent further damage.

6.6 Using the Recommended Transmission Fluid

Using the recommended transmission fluid is crucial for maintaining the proper operation of your Subaru’s transmission. Using the wrong type of fluid can lead to poor performance and damage to transmission components. Consult your owner’s manual or a qualified mechanic to determine the correct type of fluid for your vehicle.

7. Understanding Subaru Transmission Types

Subaru vehicles are known for their unique transmission systems, which play a crucial role in their performance and handling. Understanding the different types of transmissions used in Subaru vehicles can help you maintain and troubleshoot your vehicle more effectively.

7.1 Automatic Transmissions (AT)

Automatic transmissions are the most common type of transmission used in Subaru vehicles. They offer convenience and ease of use, automatically shifting gears based on the vehicle’s speed and load. Subaru automatic transmissions are known for their reliability and smooth shifting performance.

7.2 Continuously Variable Transmissions (CVT)

Continuously Variable Transmissions (CVT) are becoming increasingly popular in Subaru vehicles. CVTs offer improved fuel efficiency and smoother acceleration compared to traditional automatic transmissions. They use a belt and pulley system to provide a seamless range of gear ratios.

7.3 Manual Transmissions (MT)

Manual transmissions are less common in Subaru vehicles but are still available in some models. Manual transmissions offer greater control and driver engagement, allowing the driver to manually shift gears. Subaru manual transmissions are known for their durability and precise shifting feel.

7.4 Transmission Features Specific to Subaru

Subaru vehicles often feature unique transmission technologies, such as Vehicle Dynamics Control (VDC) and Active Torque Vectoring. These technologies enhance handling and stability, providing a more engaging driving experience. Understanding these features can help you troubleshoot transmission-related issues more effectively.

8. The Role of All-Wheel Drive (AWD) in Subaru Transmissions

Subaru vehicles are renowned for their Symmetrical All-Wheel Drive (AWD) system, which is integrated with the transmission to provide superior traction and handling in various driving conditions. Understanding the role of AWD in Subaru transmissions is crucial for maintaining and troubleshooting your vehicle.

8.1 Symmetrical All-Wheel Drive (AWD) System

Subaru’s Symmetrical AWD system distributes power evenly to all four wheels, providing maximum traction and stability. This system is integrated with the transmission to ensure that power is delivered efficiently and effectively. The Symmetrical AWD system is a key factor in Subaru’s reputation for safety and performance.

8.2 AWD and Transmission Compatibility

The AWD system and transmission must be compatible to ensure proper operation. Using the wrong type of transmission fluid or performing incorrect repairs can damage the AWD system and lead to performance issues. Consult your owner’s manual or a qualified mechanic to ensure that the AWD system and transmission are properly maintained.

8.3 Maintaining AWD Components

Maintaining the AWD components is essential for preserving the performance and reliability of your Subaru. Regular inspection and lubrication of the AWD components can prevent wear and tear. Follow the manufacturer’s recommended maintenance schedule for AWD components to keep your Subaru running smoothly.

9. Resources for Subaru Owners

Accessing reliable resources is crucial for Subaru owners looking to maintain and troubleshoot their vehicles. Here are some valuable resources that can help you keep your Subaru running smoothly:

9.1 Subaru Owner’s Manual

The Subaru owner’s manual is a comprehensive guide to your vehicle’s features, maintenance requirements, and troubleshooting tips. It provides detailed information on the transmission, AWD system, and other critical components. Refer to the owner’s manual for specific maintenance recommendations and troubleshooting procedures.

9.2 Online Forums and Communities

Online forums and communities are valuable resources for Subaru owners looking to share information, ask questions, and get advice from other owners. These forums can provide insights into common issues and DIY solutions. Participate in online forums to learn from other Subaru owners and share your own experiences.

9.3 Certified Subaru Mechanics

Certified Subaru mechanics have the training and expertise to diagnose and repair Subaru vehicles. They can provide accurate diagnoses and perform repairs using genuine Subaru parts. Consult a certified Subaru mechanic for complex issues or repairs that require specialized knowledge and equipment.

9.4 Online Parts Retailers

Online parts retailers offer a wide selection of genuine Subaru parts and aftermarket components. They can provide competitive prices and convenient online ordering. Research online parts retailers to find the best deals on transmission fluid, temperature sensors, solenoids, and other essential parts.

9.5 Local Auto Parts Stores

Local auto parts stores offer a convenient source of parts and supplies for Subaru owners. They can provide expert advice and assistance in selecting the right parts for your vehicle. Visit your local auto parts store for transmission fluid, filters, sensors, and other essential maintenance items.

10. FAQs About Subaru AT Temp Light Issues

Addressing frequently asked questions can help Subaru owners better understand and troubleshoot AT Temp light issues. Here are some common questions and answers:

10.1 What Does It Mean When My Subaru AT Temp Light Is Flashing?

A flashing Subaru AT Temp light indicates that the Transmission Control Module (TCM) has detected a fault within the automatic transmission system. This warning signifies a potential issue that needs immediate attention to prevent further damage.

10.2 Can I Still Drive My Subaru With the AT Temp Light Flashing?

It is generally not recommended to drive your Subaru with the AT Temp light flashing, as it indicates a potential transmission issue. Driving with an unresolved problem can lead to further damage and costly repairs. If you must drive, do so with caution and have the vehicle inspected by a qualified mechanic as soon as possible.

10.3 How Do I Check My Subaru’s Transmission Fluid Level?

To check your Subaru’s transmission fluid level, locate the transmission fluid dipstick, usually marked with a transmission symbol. Remove the dipstick, wipe it clean, and reinsert it fully. Pull it out again to check the fluid level. It should be between the “Min” and “Max” marks.

10.4 What Type of Transmission Fluid Does My Subaru Need?

The type of transmission fluid your Subaru needs depends on the specific model and year. Consult your owner’s manual or a qualified mechanic to determine the correct type of fluid for your vehicle. Using the wrong type of fluid can lead to poor performance and damage to transmission components.

10.5 How Often Should I Change My Subaru’s Transmission Fluid?

The recommended interval for changing your Subaru’s transmission fluid depends on the specific model and driving conditions. Consult your owner’s manual for the manufacturer’s recommended maintenance schedule. Typically, transmission fluid should be changed every 30,000 to 60,000 miles.

10.6 What Are Some Common Causes of a Flashing Subaru AT Temp Light?

Common causes of a flashing Subaru AT Temp light include low transmission fluid level, overheating transmission, faulty temperature sensor, issues with solenoids, and damaged wiring or connectors.

10.7 Can a Faulty Temperature Sensor Cause the AT Temp Light to Flash?

Yes, a faulty temperature sensor can send incorrect readings to the TCM, causing the AT Temp light to flash even if the transmission is not actually overheating. Replacing the temperature sensor may be necessary to resolve the issue.

10.8 How Do I Read the Trouble Codes on My Subaru?

To read the trouble codes on your Subaru, you’ll need an OBD-II scanner. Plug the scanner into the OBD-II port under the dashboard, turn on the ignition, and follow the scanner’s instructions to read the stored trouble codes.

10.9 Can I Replace the Transmission Temperature Sensor Myself?

Yes, replacing the transmission temperature sensor is a relatively simple DIY task that can resolve a flashing AT Temp light caused by a faulty sensor. Follow the steps outlined in Section 4.2 to replace the sensor yourself.

10.10 When Should I Seek Professional Help for My Subaru’s Transmission Issues?

You should seek professional help for your Subaru’s transmission issues if you encounter complex diagnostic codes, persistent problems after DIY attempts, unusual transmission noises or behavior, lack of experience or tools, or warranty considerations.

Having the Subaru AT Temp light blinking can be stressful. By understanding what it means, potential causes, diagnostic steps, and DIY solutions, you’re better equipped to address the issue. Regular maintenance and prompt attention to warning signs can help prevent costly transmission repairs.

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