There are a variety of scenarios that can make your check AWD light come on. It is important to note that if your AWD system turns off, it is most likely because the car is trying to prevent further damage to itself or when you have temporarily changed the wheels of your vehicle to a spare. Here are a few reasons why the AWD light, in particular, might come on:
Remember that the AWD system transfers power from the engine to the tires? The transfer case and gearbox are the combinations in the car that make this possible. Typically, transfer switch settings make it possible to drive on the road. When the transfer case sensor selector has issues, the switch would most likely get stuck to one position and not shift at all.
As mentioned before, your tire size is important in the equalization and function of your AWD. If the tire is too small or just doesn’t cut it, the sensor may fail to respond due to a viscous coupling and malfunctioning differentials.
If you’re driving a sports vehicle, the chances are that you have taken it for a spin in extremely muddy or wet conditions. This won’t exactly cause a problem in the system but would cause a problem in the wiring, causing the warning to come on.
Hydraulic pressure is needed for the functionality of the AWD, and therefore there can be no leaks. Shaft seals are the ones that keep leaks from manifesting. If you have a shaft seal problem, you should have it repaired by a car mechanic.
Fixing transfer sensor problems is easy (it’s happened to me twice in three years). You take the negative battery cable off and press the start button to get the residual power in the system out. You then take the key out and put the cable back on the battery. This method works most times.
While indirect problems of the transfer sensor like those above might cause a problem, it is also possible for problems within the sensor itself to arise. The sensor is prone to failure or might have loose wires after you’ve driven the car for a while.
The best thing to do is replace the sensor or take the car to the mechanic and troubleshoot using an OBD scanner. Sensor replacements cost around $20 to $80. You could also try to switch off the vehicle and disconnect the battery after a while to check if the error message goes away. If it doesn’t, refer to the solutions mentioned above.
Chances are, if the check engine light is on as well, the car will turn off the AWD itself to prevent further damage. This is necessary, and it is the car’s way of telling you that you have to fix the problem with the engine before the AWD (which you need to). Problems causing this might include:
When the gas cap is faulty or loose, it will allow pollutants to leak into your fuel tank, causing cold running or a bad fuel economy through evaporation. The best thing to do is tighten the gas cap if it’s loose. After driving for about a hundred miles, the light should go off by itself if this was the problem.
Should the problem persist, the only alternative is to whip out your OBD scanner and read the codes. The Check Engine light is responsible for any problem with your engine and beyond, which can be rather difficult to diagnose by yourself.
The only thing to do is to check for possible causes and fix them (possible causes have been discussed, and if you don’t think any of your issues fall into the category, you should take your vehicle to a mechanic). Your AWD is a prime function you should not allow to stay (potentially) damaged.
If you are fine with the 2WD function, you can. However, the AWD problem (especially if the check engine light is on) is indicative of a much deeper problem than just the AWD system, so you should fix or attempt to fix it before driving.
All Toyota Highlanders are equipped with a lock AWD button. To turn on the lock mode, press this button, which will make a suspension-like icon come up on your dashboard. This will lock the center differential and distribute torque evenly across all wheels.
After you have used this button, you press the lock button back to turn it off. The system would also automatically turn off when the car exceeds 25 mph or when the brake is engaged to ensure that the ABS can do its jobs easily.
While the AWD warning message can be caused by simple things like a loose gas cap or moisture, there are more serious problems as well that can cause it. It is always recommended to start checking the easy things, and progress to more complex tasks like checking the transfer case shaft for a seal failure.
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