All-wheel drive (AWD) systems send power to all four wheels. AWD is found on many modern vehicles, especially in areas that tend to experience poor weather conditions in the winter. If there is a problem with the AWD system, you will often see a message that says “Check AWD System” or something similar.
Not sure where to start? Keep reading to understand what this warning means, what can cause it to appear, and what you should do if this message shows up.
“Check AWD System” Meaning
If you see the message “Check AWD System” appear in the instrument cluster, it indicates that there is a problem with the all-wheel drive system of your vehicle, whether it’s a Toyota Highlander, RAV4, Lexus RX350, or other.
While most common in Toyota and Lexus models, other car manufacturers use similar messages to convey issues with the AWD system. You may see a message that says “R.DIFF TEMP”, a check engine light, “Check AWD System” or simply “AWD”.
Causes of AWD System Issues
1) Overheated Differential
An overheated differential is a fairly common trigger for AWD system warnings. Differentials may overheat when you drive the car on mismatched tires, or when driven hard for long periods of time. You are more likely to overheat the differential in hot weather and extreme driving conditions.
2) Low or Old Transmission or Differential Fluid
If your differential fluid is old, too low, or the wrong type, parts inside the differential or transaxle will not be lubricated properly. This may lead to increased wear, slipping, grinding, clunking, and other unusual feelings as you drive.
If you’ve recently replaced your transmission or differential fluid and start to notice these issues, verify that you’ve replaced the fluid with the correct specification. Your owner’s manual should have a list of specifications you need to follow for each type of fluid.
3) Mismatched Tires
AWD systems tend to be more sensitive to differences in tire diameter. This is because many all wheel drive systems are implemented using one or more limited slip differentials. As these limited slip differentials work to limit wheel slip, they produce heat. Excessive heat can wear out the differential prematurely.
Limited slip differentials have to work harder when the wheels are spinning at different speeds for long periods of time, as they would be when the tire diameters do not all match. If you find one or more tires is mismatched, you can sometimes find a tire shop that will shave a tire down so the tread depth matches across all four tires.
Always remember to rotate your tires so you don’t end up in this situation. Rotating your tires is fairly inexpensive, but replacing part of an AWD system will cost you a lot of money if this maintenance task is neglected.
4) Transmission Problems
Transmissions are critical parts of the powertrain that transfer power to each of the differentials in an AWD system. Many front and center differentials are integrated into the transmission housing. This is often called a transaxle by the manufacturer.
Transmission problems can cause a number of problems for the AWD system, including trouble shifting, transmission slipping, and grinding. Unfortunately many transmission problems are expensive repairs.
5) Problems with Traction Control or Stability Control Systems
Not all AWD systems work the same way. Some vehicles heavily lean on their traction or stability control systems to limit wheel slip. If you are having problems with your traction control or stability control systems, you are likely to see an AWD warning on the dash as well.
Traction Control and Stability Control systems are mostly electronic, but they make heavy use of the wheel speed sensors (also called ABS sensors). Make sure your wheel speed sensors are working correctly. You can check your wheel speed using a high quality scan tool.
6) Disconnected Sensors, Wiring Issue, Bad Ground
Sometimes the cause of an AWD system problem can be as simple as a disconnected sensor or wiring issue. Modern AWD systems use fancy electronics and software to monitor and control the AWD system. Some AWD systems use the brakes to control wheel slip, which is cheaper and easier to implement than a limited slip differential.
A sensor that is unplugged, a wire with worn insulation, or a bad ground can throw an AWD system warning if the ECU detects erroneous input. Although wiring issues can be a huge headache, finding a sensor that is unplugged is fairly straightforward if you have a factory service manual.
If you were just in there doing some work, it’s often pretty easy to retrace your steps to make sure you didn’t forget to plug anything back in after your maintenance tasks were completed.
7) Problems with an Electric Motor or Hybrid Battery
Some hybrid vehicles use a gas engine for one axle and an electric motor for the other. Electric vehicles may use dual motors: one motor for each axle of the vehicle. If there is an issue with an electric motor or the hybrid battery, one or more axles may not receive power.
If you have an issue with the hybrid battery or an electric motor, you should see an additional warning on the dash indicating this issue. Hybrid batteries may go bad over time, but they are replaceable. Unfortunately, the cost to replace a hybrid battery can be extremely expensive.
Frequently Asked Questions
What Should I Do if the AWD System Warning Light Comes On?
If the AWD system warning light comes on, it’s important to have your vehicle inspected as soon as possible. As noted above, the warning light can indicate a variety of issues, with some being more severe than others.
If you have access to an OBD2 scanner, use it to see what fault codes are stored in the ECM that may be causing the AWD warning light to illuminate and go from there. Otherwise, make an appointment with your local dealership or a good, independent mechanic that specializes in your brand of vehicle.
Can I Still Drive My Vehicle if the “Check AWD System” Light Is On?
It is not recommended to drive your vehicle when it’s letting you know there’s a problem with the AWD system. Continuing to drive your vehicle with the AWD light on can cause further damage to your vehicle and potentially put you and your passengers at risk.
How Often Should I Have My AWD System Checked?
It is recommended to have your AWD system checked at least once a year or as recommended by your vehicle’s manufacturer. Regular maintenance and inspections can help prevent issues with your AWD system and make sure that it is functioning as it is supposed to.
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