Electric Power Steering Assist Reduced
What does TESLA-STEERING_A020 mean?
The TESLA-STEERING_A020 (Tesla EPS Controller) EV fault code means: Electric Power Steering Assist Reduced. This is a serious severity code.
Common Symptoms
- Touchscreen or instrument cluster shows a steering warning or 'Steering Assist Reduced' alert
- Steering wheel feels noticeably heavier than usual, especially at low speeds or while parking
- Effort required to turn the wheel increases suddenly or gradually during a drive
- Warning persists after restarting the car, or comes and goes intermittently
- 12V battery or low voltage alert appears alongside the steering warning
- Car may limit Autopilot or Autosteer availability while this fault is active
- Steering feels normal at highway speeds but unusually stiff during slow maneuvers or parking
Probable Causes (Ranked by Likelihood)
- 12V battery or DC-DC converter voltage drop below the EPS module's minimum operating threshold Very Likely
- EPS module overheating due to extended low-speed maneuvering, hot ambient conditions, or blocked thermal path Very Likely
- EPS module internal fault or degraded power stage requiring replacement or reinitialization Likely
- CAN bus communication fault between VCFRONT and the EPS controller causing a protective derate Likely
- Steering angle sensor (SAS) out of calibration or reporting implausible values Possible
- Corroded or loose 12V power or ground connection at the EPS module or underhood junction box Possible
- Software or firmware mismatch on the EPS or VCFRONT controller after an OTA update Less Likely
Step-by-Step Diagnostic Procedure
Start with the 12V system. Open the trunk (Model 3/Y) or front trunk (Model S/X) and locate the 12V battery. Measure voltage with a multimeter. You want 12.4V or higher at rest. Below 12.0V under no load is a red flag. If the car is a newer lithium 12V model (post-2021 Model S/X, post-2022 Model 3/Y), the battery can fail suddenly without warning.
Check whether the alert appeared after extended low-speed driving, tight parking maneuvers, or in very high ambient temperatures. If so, pull over and let the car sit with climate off for 10 to 15 minutes. EPS thermal protection will often clear STEERING_a020 once the module cools. Restart the car and see if the alert clears.
Open the Scan My Tesla app with an OBDLink MX+ or Veepeak adapter plugged into the CAN port. Pull live 12V bus voltage while the car is driving. Voltage should stay between 13.5V and 14.5V when the DC-DC converter is active. A reading below 12.8V under load points to a weak 12V battery or a failing DC-DC converter.
Inspect the EPS module wiring harness connector. On Model 3/Y it is accessible under the frunk with the front fascia partially removed. Look for corrosion, bent pins, or a connector that has partially unseated. Wiggle the connector with the car in a safe state and note whether the alert changes.
Perform a soft reboot by holding both scroll wheel buttons simultaneously until the touchscreen goes black and the Tesla logo appears. After the reboot, check whether the alert returns. A reboot clears transient CAN bus communication faults that can trigger a protective steering derate.
Check for any pending OTA software updates. Go to Software in the touchscreen menu. If an update is waiting, install it. Known EPS firmware bugs in several Model 3 and Model Y production windows were resolved via OTA. Applying a pending update takes 20 to 45 minutes.
If the fault persists after addressing 12V voltage and ruling out thermal causes, the EPS module itself may need replacement or re-flashing. This requires Tesla Toolbox 3 (dealer-only) to reinitialize the new module and calibrate the SAS. Schedule a service appointment. DIY replacement without Toolbox 3 calibration will not resolve the fault and may leave steering worse.
Frequently Asked Questions
What does Tesla code STEERING_a020 mean?
It means the electric power steering system has reduced how much assist it provides to you. The steering still works mechanically, but the motor that makes it feel light and easy is either running in a protective reduced-output mode or has partially faulted. The most common triggers are a weak 12V battery, the EPS module getting too hot after extended low-speed driving, or a CAN bus communication hiccup between the steering controller and the front vehicle controller.
Can I still drive the car with STEERING_a020 active?
Yes, but with caution. The car will move and steer, but it will feel noticeably heavier, especially at low speeds and in parking situations. Highway driving at speed is less affected. Do not rely on Autopilot or Autosteer while this fault is active, as Tesla typically blocks those features when a steering fault is present. Drive carefully and address the fault as soon as possible.
How much does it cost to fix STEERING_a020?
If the cause is a weak 12V battery, you are looking at $150 to $400 for the battery depending on model and whether you do it yourself. If it is a thermal event, the fix is free. Just let the car cool down. If the EPS module has actually failed, expect $800 to $2,500 at a shop, with most of that being the module cost and the required calibration procedure that only Tesla Toolbox 3 can perform.
Will STEERING_a020 clear on its own?
Sometimes yes, sometimes no. If it was triggered by heat buildup during parking maneuvers or low-speed driving, it will usually clear after the car cools and you restart. If it was caused by a 12V voltage dip that has since recovered, it may also clear on a reboot. If the EPS module has a hard internal fault, the code will come back every drive cycle and will not clear without professional diagnosis and likely module replacement.