If you’re driving a Toyota Highlander and notice that the DAC (Downhill Assist Control) is not available, you’re probably seeking answers. You may have come across this feature in other SUVs or Toyota models and are now wondering why your Highlander seems to lack it—or why the system intermittently disables itself. In this article, we will explore what DAC is, why it might not be available in your vehicle, and what alternatives or solutions exist.
Understanding Downhill Assist Control (DAC)
Before diving into the reasons behind the DAC’s absence or inactivity, it’s essential to understand what the Downhill Assist Control system does and why it matters.
What Is DAC?
DAC, or Downhill Assist Control, is a Toyota-developed electronic driving aid designed to help drivers descend steep slopes safely, especially on off-road or rough terrain. It uses the vehicle’s antilock braking system (ABS) to control wheel speed, preventing loss of traction and maintaining a steady, low vehicle speed without requiring constant pressure on the brake pedal.
- Engages automatically at speeds below 15 mph
- Uses the ABS system to modulate wheel speed
- Requires specific steering angle input to activate
When Should DAC Be Used?
DAC excels in situations such as:
Steep Gravel Roads
Keeping control on uneven surfaces becomes easier with DAC’s automatic modulation of braking.
Rocky or Muddy Descents
Because the terrain can be slippery and unpredictable, DAC helps maintain traction and control.
Off-road Enthusiasts
For those who frequently drive off the paved road, DAC is a valuable safety and convenience feature.
Why Is DAC Not Available in My Toyota Highlander?
Now that we understand what DAC is, let’s explore the key reasons the feature might not be working—or might not exist at all—on your Toyota Highlander.
1. DAC Is Not Included in All Highlander Trim Levels
The Toyota Highlander lineup offers various trim levels, and not every trim includes the DAC feature. If you’re not driving the highest or off-road-ready configurations, you may not have access to DAC.
Trim Level Comparison
| Trim Level | DAC Availability | Notes |
|---|---|---|
| LE | No | Economy-focused trim |
| XLE | No | Mid-tier, comfort-oriented |
| XSE | No | Sport-tuned suspension, not built for off-road |
| Platinum | No (usually) | Luxury focus, not off-road capability |
| Trail | Yes | Special off-road edition with all-terrain features |
If your Highlander is not a Trail trim, chances are DAC is not available at all. The Trail trim was introduced to add a degree of off-road ability to this popular SUV, especially to compete with other midsize crossovers that include features like hill descent assist.
2. The Highlander Trail Trim May Not Be Available in All Markets
Even if you’re interested in DAC, Toyota does not sell the Trail trim in all regions. This can be due to:
- Demand fluctuations
- Production limitations
- Dealership-specific stock issues
Owners outside of the U.S. or in markets where off-road capability is less in demand might not be able to access the Trail trim at all—thus, no DAC access by default.
3. Issues with DAC Deactivation or Malfunction
If your Highlander is a Trail trim, but DAC isn’t working or displays a message like “DAC not available” or “Hill Descent Control not available”, then there could be an issue triggering or sustaining DAC activation.
Let’s break down common reasons for DAC malfunction or deactivation.
Incorrect Speed Threshold
DAC works only below a set speed, usually 15–18 mph. If the vehicle is moving too fast, it won’t engage.
Steering Wheel Angle and Position
To activate DAC, a certain amount of steering input is required. If the driver doesn’t turn the steering wheel far enough (left or right), the system won’t recognize that the vehicle is approaching a downhill off-road situation.
Vehicle Stability Control (VSC) Interference
If VSC or Traction Control sensors detect an issue or the system has automatically turned off, DAC will not function until VSC is re-enabled.
Transmission Not in Low Range or First Gear
Some models require the transmission to be in a low gear for DAC to activate properly. If in automatic overdrive, DAC may be disabled.
Brake or Throttle Input Overrides
Even after successful DAC activation, any input from the driver on the accelerator or brake pedal will deactivate it. The system assumes manual control is taken.
4. Problems in the ABS or Sensor System
DAC relies heavily on the ABS module and wheel speed sensors. If there’s a fault in the ABS system—such as a sensor failure or module error—DAC could be disabled permanently or intermittently.
Possible Components Affecting DAC
| Component | Role in DAC |
|---|---|
| Wheel Speed Sensors | Detect speed and traction loss |
| Brake Pressure Modulator Valve | Controls braking force between wheels |
| Gyro Sensor (for Stability Control) | Detects vehicle orientation and tilt |
| Electronic Brake Control Module (EBCM) | Central hub that integrates all signals before DAC can trigger |
A malfunction in any of these components could trigger a “DAC not available” message or cause intermittent behavior during descents.
5. Driving on Pavement or Flat Terrain
You might be tempted to engage DAC while driving on paved uphill/downhill roads, perhaps to reduce brake wear or conserve effort. However, DAC is designed to work primarily on off-road or uneven terrain.
If you’re trying to engage DAC on asphalt or under normal driving conditions, it won’t activate. That can be misleading if you’re not aware of the context in which DAC is supposed to be used.
Troubleshooting and Fixes for a Non-Working DAC System
If you’re experiencing a “DAC not available” message or a system that keeps disabling itself, you’re not stuck. Here’s how to diagnose and address the issue.
Step 1: Verify the Trim Level
Double-check whether your Toyota Highlander is the Trail trim, or a lower trim without DAC. The Trail edition is generally the only trim with DAC. If you own an LE, XLE, or Platinum, simply know that:
DAC is not available as part of your vehicle’s package at all.
You would need to consider resale or switching trims if this feature is essential in your driving style.
Step 2: Check the Driving Conditions
If DAC won’t engage on a paved, flat road, that’s expected behavior. Always try activating it while slowly descending hills on loose, uneven terrain—like gravel, dirt, or a rocky path.
Step 3: Reset the System
Sometimes, a temporary glitch will disable DAC. Turning off the car, waiting a few minutes, and restarting can clear out any temporary ECU errors that might be suppressing the activation.
Step 4: Scan for Error Codes
If DAC keeps failing to engage or intermittently disables itself despite correct driving conditions, have a certified technician perform an OBD-II scan. The ABS module and DAC system might have generated diagnostic codes related to failed sensors, software issues, or communication errors in the CAN bus.
Step 5: Update Software or BCM
Modern Toyota systems rely heavily on ECU software for control features. A software update, particularly to the brake control module, might be required to enable bug-free DAC access. This is especially relevant for early Trail trim models.
What If My Highlander Doesn’t Have DAC?
If your Highlander truly doesn’t come with DAC—perhaps due to trim restrictions—there are alternatives and mitigation strategies:
What’s the Equivalent Feature in Non-Trail Highlanders?
While traditional DAC is absent from non-Trail Highlanders, the Slope-Activated Downhill Assist and Traction Control System (TRAC) in the Toyota Star Safety System™ do a decent job of holding speeds during descents.
Vehicle Stability Control (VSC) and the Antilock Brake System (ABS) help manage both traction and wheel lock during hill descents, acting as a pseudo DAC by reducing the need for manual braking.
How Drivers Can Compensate Manually
In the absence of DAC, experienced drivers can learn manual descent techniques:
- Use low gear to reduce speed on a slope
- Gently apply and release the brake to prevent skidding
- Maintain steady throttle and avoid sudden directional changes
It’s not as safe as DAC, but if you don’t frequently drive in off-road situations, these techniques will suffice.
Aftermarket Solutions
While not common, some aftermarket kits target hill descent control for SUVs and crossovers. However, for safety and retaining vehicle warranty, strongly avoid installing unrecognised or non-certified third-party DAC systems. They can interfere with factory-designed systems or even void liability insurance coverage.
Conclusion: Know Your Highlander and Its Capabilities
The DAC not available issue in Toyota Highlanders can stem from multiple sources: trim-specific feature restrictions, system errors, software issues, or inappropriate driving conditions. If you’re interested in this feature, investing in the Trail trim offers the best solution. For current Highlander owners, verifying trim features upon purchasing is critical to avoid confusion.
Understanding whether your high-mileage or family-focused SUV includes DAC or not is not just a question of luxury—it’s a matter of safety and performance under tough driving conditions. Ensure that your vehicle matches your needs, and when uncertain, consult a dealership or certified technician for clarity.
Knowledge empowers confidence. Armed with this guide, you now understand:
- Why DAC might not be available
- How to diagnose DAC-related issues
- What you can do if DAC isn’t factory-fitted
Ultimately, staying informed and proactive ensures a safer and more capable driving experience—whether you’re rolling through pavement or navigating rocky hillsides.
What is DAC and why is it important in a Toyota Highlander?
DAC, or Downhill Assist Control, is a feature designed to help drivers navigate steep declines more safely by automatically controlling the vehicle’s speed. It works by applying the brakes individually, allowing the driver to focus solely on steering. This system is especially valuable in challenging terrain, off-road conditions, or during heavy braking events where maintaining control is critical. In Toyota vehicles, including the Highlander, DAC can be an important aid for drivers who frequently travel through hilly or rugged areas.
However, not all Highlander trims or model years come equipped with DAC as standard. This is because DAC is typically included in all-wheel-drive (AWD) models and certain higher trim levels that are designed for enhanced performance in diverse driving conditions. If your Highlander doesn’t have DAC, it could be because it is a front-wheel-drive model or a lower trim package that doesn’t support the system. Understanding this distinction can help you make informed decisions about your current vehicle or potential upgrades.
Why would my Toyota Highlander not include DAC?
Toyota equips DAC only on specific models and trim levels, primarily those with all-wheel drive. If your Toyota Highlander does not have DAC, the most likely reason is that it was manufactured as a front-wheel-drive (FWD) vehicle. DAC is generally included in vehicles that are designed to handle more challenging terrain, meaning AWD models are the primary candidates for having this system.
Another possible reason is the trim level. Lower trims or older model years may lack DAC because it is bundled with other advanced driving technologies. Additionally, the feature might not be included in certain model years due to production cost adjustments or regional variations in equipment. If DAC was not included when the vehicle was manufactured, it can’t be easily retrofitted later without upgrading key drivetrain components.
Can I retrofit DAC into my existing Toyota Highlander?
Retrofitting DAC directly into a Toyota Highlander is not a simple upgrade because the system is deeply integrated with the vehicle’s drivetrain, braking system, and electronic control unit (ECU). In most cases, the DAC system cannot be added unless the vehicle already has the necessary hardware components, including AWD and compatible software in the ECU. Even then, the addition of DAC would likely require a visit to an authorized Toyota dealer for reprogramming or installation of upgraded modules.
If your Highlander is a front-wheel-drive model, retrofitting DAC is not viable without converting the drivetrain to all-wheel drive, a costly and complex procedure that often doesn’t justify the benefits. Instead, consider alternative ways to improve control on hills, such as driving techniques or investing in an AWD-compatible model in the future if enhanced downhill stability is critical to your driving needs.
Which Toyota Highlander trims and model years include DAC?
DAC is commonly available on all-wheel-drive versions of the Toyota Highlander, particularly in higher trim levels like the Limited, Platinum, or Hybrid models across several generations. Starting from the third generation (2014–2019) and continuing into the current 2020-and-later models, AWD-equipped Highlanders increasingly feature DAC, especially when paired with the CRAWL Control system and terrain mode selection. It’s important to verify the specifications of your vehicle’s exact trim, engine type, and drivetrain configuration to determine DAC availability.
The best way to confirm whether your vehicle should include DAC is to consult the original window sticker, known as the Monroney label, or your vehicle’s Vehicle Identification Number (VIN) through Toyota’s official online resources. Additionally, visiting a local Toyota dealership or contacting Toyota customer support can provide you with accurate and model-specific information based on your Highlander’s production details.
Are there other features similar to DAC in the Toyota Highlander?
While DAC is specifically designed for downhill stability, the Toyota Highlander offers several other safety and driver assistance features that enhance control in challenging driving conditions. These include Vehicle Stability Control (VSC), Traction Control (TRAC), and the Anti-lock Brake System (ABS), which work together to maintain control in slippery or uneven driving conditions. Additionally, the newer Highlander models feature advanced driving modes like Auto, Eco, Sport, and Custom Off-Road settings, which optimize performance based on terrain.
The Highlander Hybrid also includes regenerative braking and enhanced hill descent features as part of its drive-by-wire system. Although these may not provide the exact functionality of DAC, they do contribute significantly to driver confidence during descent. For off-road enthusiasts or those frequently navigating steep inclines and declines, opting for an all-wheel-drive model with the latest available driver-assist packages can offer a similar level of support and control.
Is DAC necessary for everyday driving in a Toyota Highlander?
In most everyday driving scenarios, DAC is not a necessary feature. The Toyota Highlander is primarily designed to be an SUV that balances comfort, space, and versatility for urban and suburban environments. For typical driving conditions, standard driver assistance systems such as ABS, VSC, and TRAC provide sufficient traction and stability control. Hence, many owners may go years without encountering a situation where DAC would be required.
However, if you regularly drive in mountainous regions, frequently take part in outdoor adventures, or tow heavy loads down steep grades, DAC can be a highly beneficial feature. In these cases, it can reduce brake wear and improve safety by maintaining a controlled descent. Choosing an AWD model with DAC is more ideal for those applications, allowing drivers to manage steep or slippery descents with greater peace of mind.
How can I check if my Toyota Highlander is eligible for DAC?
To determine whether your Toyota Highlander is eligible for DAC, start by checking your vehicle’s drivetrain—DAC is exclusive to all-wheel-drive models. You can verify your vehicle type and trim level through your owner’s manual, vehicle documentation, or by entering your VIN into Toyota’s official website or my.toyota.com portal. These resources will allow you to review the specific factory-installed features of your Highlander.
If you’re unclear about your trim level or vehicle configuration, visiting a Toyota dealership with your VIN can help you get an accurate report of your Highlander’s specs. Technicians can also determine if your system is compatible with any software upgrades that support DAC functionality. If DAC was not originally installed, upgrading to a compatible AWD model or higher trim may be the most direct way to access this feature while ensuring long-term usability and value.