C1741 on 2015-2018 Subaru Legacy: VDC System Fault Causes and Fixes

What's Unique About the 2015-2018 Subaru LEGACY

For this generation of Subaru Legacy, the C1741 code is a well-documented platform quirk rather than a sign of a failed part. Subaru of America issued a Technical Service Bulletin (TSB 06-77-20R) acknowledging that the VDC control module's software was overly sensitive. The official remedy is a software re-flash, making this a known issue with a specific, manufacturer-provided solution. The same TSB also applies to the 2015-2018 Subaru Outback and 2016-2018 WRX, which share the same VDC system logic.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• VDC (Vehicle Dynamics Control) warning light is on
• Hill Holder warning light is on
• Hill Holder system cancellation alarm may sound
• Cruise control may be disabled as a fail-safe
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Most Likely Causes

1. Vehicle Dynamics Control Module (VDCCM) Software Requires Update 🔴 High Probability The original factory software was too sensitive and could falsely detect a fault when the brake pedal is lightly pressed without activating the brake lights, as documented by Subaru in TSB 06-77-20R.
   How to confirm: A Subaru dealer or a shop with a Subaru Select Monitor (SSM) can check the current software calibration ID of the VDCCM and confirm if the update specified in TSB 06-77-20R is applicable and has not already been performed.
   Typical fix: Reprogramming the VDCCM with the updated software files provided by Subaru. The dealer uses their FlashWrite procedure, which requires a stable power supply from a specific Midtronics charger to prevent module failure during the flash.
   Est. part cost: $0
2. Failed Vehicle Dynamics Control Module (VDCCM) ⚪ Low Probability
   How to confirm: If the code returns after the software has been updated, or if the module is unresponsive and fails communication tests (power, ground, and CAN bus checks are good), the module itself is likely faulty. This should only be considered after the TSB has been performed.
   Typical fix: Replace the Vehicle Dynamics Control Module (which is often integrated with the ABS hydraulic unit) and perform any necessary calibration procedures.
   Est. part cost: $800-$1500

Rare But Worth Checking

• Low Battery Voltage or Poor Connection:
• Faulty or Misadjusted Brake Light Switch:

Diagnosis Steps

1. Confirm the presence of code C1741 using an OBD-II scanner capable of reading Chassis (C-prefix) codes.
2. Check for the presence of any other codes, particularly C1531, which is often related.
3. Reference Subaru Technical Service Bulletin (TSB) #06-77-20R, which directly addresses this code for 2015-18 Legacy/Outback and 2016-18 WRX models.
4. Take the vehicle to a Subaru dealership or a qualified independent shop with Subaru-specific tools (SSM or J2534 pass-through).
5. Request the shop to verify the current VDCCM software version and perform the reprogramming as detailed in TSB 06-77-20R if it's outdated.
6. If the reprogramming is completed and the code returns, diagnosis should proceed to checking the VDCCM's wiring, power, and ground connections, and CAN bus communication integrity.
7. As part of the wiring check, verify the brake light switch is functioning and adjusted correctly. Pedal stroke to activate the switch should be 5.5mm +/- 2.5mm.
8. If all connections and communications are good and the code persists after the update, the VDCCM itself is the likely point of failure and requires replacement.

Parts You'll Likely Need

• Vehicle Dynamics Control Module (VDCCM) Reprogramming (OEM #Labor Op #A567-318) — This is not a physical part, but a software update that corrects the logic flaw causing the false code, as specified by Subaru's TSB 06-77-20R.
  Trusted brands: Subaru (Dealer Service)
  OEM price range: $150-$250 (Labor)
  Aftermarket price range: N/A
• Vehicle Dynamics Control Module (VDCCM) / Hydraulic Unit Assembly (OEM #27596AL02A (superseded by 27596AL02C) or 27596AL03A (for EyeSight models, superseded by 27596AL03E)) — In the rare event that the software update does not fix the issue, the module itself may have an internal hardware failure. It is typically sold as an assembly with the ABS hydraulic unit. Part number depends on whether the vehicle has EyeSight.
  Trusted brands: Subaru (OEM)
  OEM price range: $750-$1500
  Aftermarket price range: $500-$1000 (Remanufactured)

Related Codes That Often Appear With This One

• C1531 — This code is also mentioned in TSB 06-77-20R and relates to a similar software sensitivity issue within the same VDC control module. It can be set if slight pressure is applied to the brake pedal right after releasing the Electric Parking Brake (EPB).

Technical Service Bulletins (TSBs) & Recalls

• 06-77-20R: Announces the availability of reprogramming files for the Vehicle Dynamics Control Module (VDCCM) to prevent falsely setting DTCs C1741 and C1531. It details the specific user actions (light brake pressure) that trigger the false codes and applies to 2015-18 Legacy/Outback and 2016-18 WRX models.

Platform-Specific Known Issues

• A known software issue documented in TSB 06-77-20R causes the VDCCM to set code C1741 (and sometimes C1531) incorrectly when the driver rests their foot lightly on the brake pedal.
• This issue is not unique to the Legacy and also affects the 2015-2018 Outback and 2016-2018 WRX.

Mechanic-Grade Diagnostic Values

• VDCCM Reprogramming Power Supply — expected: Steady 13.5 Volts. Failure: Voltage rising above 14V will abort the procedure. Fluctuation indicates a weak vehicle battery that needs charging or replacement before attempting the reflash.
• Brake Light Switch Activation Stroke — expected: 5.5mm +/- 2.5mm (a range of 3mm to 8mm) of pedal travel. Failure: If pedal travel before brake light activation is outside this range, the switch requires adjustment.
• VDC Ground Bolt Tightening Torque — expected: 13 N·m (9.6 ft-lb). Failure: A loose ground bolt (GB-5) can cause intermittent electrical issues for the VDC system.
• Battery Voltage (Pre-diagnostic check) — expected: 12 V or more. Failure: Voltage below 12V indicates a weak battery which can cause various electronic modules, including the VDCCM, to set fault codes.

Scan Tool Commands That Help

• Subaru Select Monitor: VDC sensor midpoint setting mode — Required after installing, replacing, or adjusting the steering wheel, suspension parts, wheel alignment, or the VDCCM itself. This function re-calibrates the neutral position for the steering angle and G sensors.
• Subaru Select Monitor: VDC Inspection Mode — This is a function check sequence that systematically tests the VDC hydraulic unit's solenoid valves and pump motor to confirm their operation without driving the vehicle.
• Subaru Select Monitor: Parameter Selection / Registration — This is mandatory after replacing the VDCCM. It configures the new module for the specific vehicle model and options. Failure to perform this will set a 'Parameter selection error' DTC.

Wiring & Ground Locations

• VDC control module & hydraulic control unit (VDCCM&H/U) — Located in the engine bay. It is the assembly with multiple brake lines attached, often near the firewall or inner fender.. This is the central computer for the VDC system that stores the C1741 code and requires the software update. Physical access is needed for replacement or connector inspection.
• Ground Bolt GB-5 — A primary ground point for the VDC system.. A loose or corroded ground connection at this point can cause erratic behavior or fault codes in the VDC system, mimicking a module failure. Checking that it is clean and torqued to 13 N·m is a key diagnostic step if the TSB reflash doesn't resolve the issue.
• Brake Light Switch — At the top of the brake pedal arm, under the driver's side dashboard.. The VDCCM relies on the signal from this switch. The C1741 TSB is triggered by light pedal pressure *not* activating the switch. A faulty or misadjusted switch can send an incorrect signal, causing VDC faults separate from the TSB software issue.

Real Owner Repair Stories

• Reddit user in r/AskMechanics (2015 Subaru Outback, 150,000 miles) — ABS light and 'no traction control' light came on immediately after performing work that involved disconnecting the steering shaft.
  ❌ Tried (didn't work) Getting a wheel alignment., A local shop wanted to disassemble the dashboard to investigate., A dealer wanted to replace the u-joint coupling and clock spring.
  ✅ What actually fixed it The user's research indicated the actual required fix was to perform a 'VDC Midpoint reset' using a scan tool. This recalibrates the steering angle sensor and G-sensors, which is necessary after mechanical steering or suspension work.

OEM Part Supersession History

• 27596AL02A → 27596AL02B, then 27596AL02C — Part revisions to improve reliability or manufacturing. This is for models without the EyeSight package.
  Heads up: These part numbers are for non-EyeSight vehicles. Using an EyeSight module (e.g., 27596AL03x series) on a non-EyeSight car, or vice-versa, will result in system incompatibility and fault codes.

Model Year Variations Within This Range

• 2015-2018: The 2018 model year received a mid-cycle refresh with cosmetic and interior updates. However, this did not change the VDC system hardware or the applicability of TSB 06-77-20R, which covers the entire 2015-2018 model year range for the Legacy.