2017-2018 Subaru Forester Power Steering Module: Failure in Cold, Programming, and Replacement

Symptoms of a Failing Power Steering Control Module

A failing power steering control module in a 2017-2018 Subaru Forester will make its presence known, often with clear and sometimes sudden symptoms. The most common sign is a change in steering effort, but other clues can point to a faulty module.

• Sudden Heavy Steering: The most dramatic symptom is a sudden and complete loss of power steering assist. The steering wheel will become very difficult to turn, similar to driving a car without the engine running. This can be intermittent, working fine one moment and failing the next.
• Power Steering Warning Light: When the module detects an internal fault, it will trigger the power steering warning light on your dashboard. This light typically looks like a steering wheel with an exclamation mark next to it.
• Increased Effort in Cold Weather: A well-documented issue for these specific models is the loss of power steering after the vehicle has been sitting in freezing temperatures. This is often caused by a relay inside the module freezing, which prevents it from working correctly on startup.
• Whining or Clicking Noises: While less common, a failing module can send erratic signals to the steering motor, causing it to make unusual clicking or whining sounds.

Associated Diagnostic Trouble Codes (DTCs)

If the power steering warning light is on, a diagnostic scan tool can retrieve fault codes. A basic OBD-II scanner may not be able to read these codes; you will likely need a more advanced tool that can communicate with the EPS module.

• C2532: This is the most specific and important code for this issue. It directly points to a fault within the Electronic Power Steering (EPS) control module, often related to the internal relay failure in cold weather.

Known Issues, TSBs, and Warranty Extensions

Subaru has acknowledged steering-related issues on these vehicles through official service documents. It's important to distinguish between problems with the control module and problems with the steering rack itself.

Technical Service Bulletin (TSB) 04-24-18: The Cold Weather Failure

This is the key document related to this module's failure. Subaru issued TSB 04-24-18 to address customer complaints of increased steering effort or total loss of assist during freezing temperatures. The cause was identified as a relay contact freezing inside the control module. The bulletin advises technicians to check for DTC C2532 and, if present, to replace the module with an updated part. The recommended replacement part is the latest version, 34710SG102.

Warranty Extension for Steering Gear Box (The Rack)

Separately, Subaru issued a warranty extension for the Electronic Power Steering Gear Box Assembly (the steering rack) on many models, including the 2014-2018 Forester. This issue involves the potential for the rack housing to crack due to corrosion in salty environments combined with a sharp impact (like hitting a pothole). This failure results in an uneven steering feel when turning, not a complete loss of assist. This is a different problem from the control module failure but is good to be aware of.

Programming and Calibration: This Step is NOT Optional

The Power Steering Control Module is integrated into the vehicle's computer network (CAN bus). When you install a replacement, you must perform a calibration procedure so the module can learn the steering angle sensor's position and communicate with other systems in the car.

• What is required: This process requires a dealer-level diagnostic tool like the Subaru Select Monitor or a high-end professional aftermarket scanner from brands like Autel. A standard code reader cannot perform this function.
• The Process: A technician uses the scan tool to access the EPS module. If using a recycled part, the first step is often to "Clear Assist Map" to erase the donor vehicle's data. Then, the technician will initiate the "Steering Angle Sensor Calibration" or "Zero Point Calibration." This procedure teaches the new module the straight-ahead position of the wheels.
• Who can do it: A Subaru dealership is the most certain option. Many independent repair shops that specialize in Japanese vehicles or have invested in advanced diagnostic tools can also perform this programming. It is not a task for a typical locksmith or a DIY mechanic without the proper scanner.

Buying a Used Power Steering Control Module

Given the high cost of a new module from the dealer, a used OEM part is an excellent, cost-effective solution. Because this is a purely electronic part with no moving components, a used module from a low-mileage vehicle is just as reliable as a new one, provided you follow these guidelines.

1. Verify the Part Number: This is the most important step. The original part numbers for the 2017-2018 Forester are 34710SG100, 34710SG101, and 34710SG102. The latest, updated version is 34710SG102, which supersedes the previous two. While any of these will work, aim for the newest version (SG102) if possible, as it contains the fix for the cold-weather failure.
2. Physical Inspection: Before installation, inspect the used module. Look for any signs of corrosion on the electrical pins or the aluminum case. Check that the plastic connector housings are not cracked or damaged. Avoid any unit that shows signs of water intrusion or physical damage.
3. Source Vehicle Information: If possible, get the mileage of the vehicle the part came from. A module from a vehicle with under 100,000 miles is ideal. However, since these are not high-wear items, mileage is less critical than ensuring the part number is correct and it shows no signs of damage.
4. Plan for Programming: Remember to factor in the cost and logistics of programming. Have a plan in place before you buy the part. Call your local dealer or a trusted independent shop, tell them you are replacing the module with a used one, and confirm they can perform the calibration.

Cost to Replace the Power Steering Control Module

The cost can vary significantly depending on whether you use new or used parts and who performs the labor and programming.

Frequently Asked Questions (FAQ)