2019-2020 Cadillac CT6 Active Rear Steering Actuator: Diagnosis and Replacement Guide

Understanding the Active Rear Steering System

The Active Steering Actuator is exclusive to 2019-2020 Cadillac CT6 models equipped with All-Wheel Drive (AWD) and the optional Active Chassis Package. If your CT6 is front-wheel drive or does not have this specific package, it will not have this part. The system's purpose is to make the large sedan feel more nimble and stable by actively steering the rear wheels. At speeds below approximately 22 mph, the rear wheels turn opposite the front wheels, reducing the turning circle. 🎬 Watch: See the CT6 active rear steering in action. Above that speed, they turn with the front wheels to provide a more planted feel on the highway.

Symptoms of a Failing Rear Steering Actuator

When the rear steering actuator begins to fail, the vehicle's computer will typically disable the system and alert the driver. The most common signs include:

• "Service Steering System" or "Service Rear Axle" Message: This is the most common indicator of a problem with the system. The message will appear on the driver information center (DIC).
• Warning Lights: The stability control or traction control warning lights may illuminate on the dashboard, as the rear steering system is integrated with these safety features.
• Heavier Steering at Low Speeds: 🎬 Watch: How to diagnose and fix heavy Cadillac steering. With the system disabled, the car may feel more difficult to maneuver in parking lots or during tight turns, as you lose the benefit of the reduced turning radius.
• Unusual Handling Characteristics: While the system is designed to fail into a safe, locked straight-ahead position, some drivers may notice a change in handling feel, especially during lane changes at highway speeds.
• Noise from the Rear: In cases of mechanical failure within the actuator, you might hear grinding or clunking noises from the rear of the vehicle, though this is less common than an electronic failure.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

As of this writing, there are no specific recalls for the Active Steering Actuator itself on the 2019-2020 Cadillac CT6. However, there are several recalls for the CT6 that relate to other vehicle systems, such as the 10-speed transmission and the Electronic Brake Control Module (EBCM), which controls the rear steering system. A software error in the EBCM, for example, could potentially affect rear steering operation. It is always wise to check with a dealership using your vehicle's VIN to see if any open recalls apply.

Forum discussions and mechanic reports suggest that electrical issues, such as damaged wiring or faulty connectors leading to the actuator, can be a cause of failure, sometimes mimicking a failure of the actuator itself. A thorough diagnosis should always include an inspection of the wiring harness leading to the unit.

Buying a Used 2019-2020 CT6 Active Steering Actuator

A used OEM actuator is a cost-effective alternative to a new part, but careful inspection is crucial. Because this is a complex electronic and mechanical part, here’s what to look for:

• Verify Part Numbers: The most important step. Known OEM part numbers are 84377326 and 84870309. Part number 84870309 is a newer version that supersedes 84377326. Always match the part number from your original unit or confirm compatibility with the seller.
• Inspect the Electrical Connector: The main electrical plug and its pins are a major potential failure point. Look for any signs of corrosion (green or white crust), bent pins, or damage to the plastic connector housing. Do not buy a part with a damaged connector.
• Check the Boots and Seals: The actuator has protective rubber boots, similar to a steering rack. Inspect these boots carefully for any rips, tears, or signs of perishing. A compromised boot allows water and dirt to enter the mechanism, leading to rapid failure.
• Look for Physical Damage: The actuator is a long, rack-like component. Inspect the main body for any cracks, dents, or signs of impact from road debris or a collision. Check that the mounting brackets are intact and not bent.
• Ask About the Donor Vehicle: If possible, get the mileage of the vehicle the part came from. A lower-mileage part is always preferable. Also, ask if the donor vehicle had any flood or collision damage, especially near the rear axle.

Replacement and Calibration

Replacing the Active Steering Actuator is a job for an experienced technician or a very skilled DIY mechanic. The process involves raising the vehicle, removing panels, and potentially lowering a portion of the rear subframe to access the actuator.

Crucially, this part requires calibration after installation. A GM-specific diagnostic scan tool (like a Tech 2 or equivalent modern tool) is needed to perform the steering angle sensor calibration. 🎬 Watch: How to reset a GM steering angle sensor. This procedure teaches the vehicle's computer the new actuator's position and ensures the system operates correctly and safely. Failure to calibrate the new part will result in continued warning lights and a non-functional system. A four-wheel alignment is also required after replacement to ensure proper vehicle tracking.

Cost of Replacement

Frequently Asked Questions (FAQ)