C0045 on 2009-2014 Subaru Legacy: ABS Communication Fault vs. Transmission Failure

What's Unique About the 2009-2014 Subaru Legacy

The 2009-2014 Legacy spans two generations, and the meaning of C0045 is critically different between them. For the 2010-2014 models equipped with the TR580 CVT, this code is a well-documented 'sympathy code' that almost always points to an internal failure of the transmission's valve body or a specific solenoid. The ABS system is simply reporting the bad data it's getting from the struggling transmission. On the 2009 model (the last year of the previous generation), the code is more likely a general communication or module fault within the ABS system itself, or potentially a wiring issue.

Generation note: The 2009 model is the fourth generation (BL/BP). The 2010-2014 models are the fifth generation (BM/BR). The most common cause for C0045 (CVT valve body failure) applies specifically to the fifth-generation models with the TR580 CVT.

Symptoms You May Notice

• ABS warning light is on
• Traction control / VDC (Vehicle Dynamics Control) light is on
• Flashing 'AT OIL TEMP' light (common on 2010-2014 models)
• Check Engine Light may be on
• Cruise control disabled or flashing
• Harsh or erratic shifting from the CVT
• Vehicle hesitates or shudders when coming to a stop

Most Likely Causes

1. Failing CVT Valve Body or Solenoid (2010-2014 models) 🔴 High Probability → Shop Transmission Valve Body The TR580 CVT used in this generation is known for issues with the valve body's solenoids, particularly the torque converter lock-up duty solenoid. This internal transmission fault causes the TCM to send invalid data to other modules, triggering the C0045 code in the ABS module.
   How to confirm: Use a capable scan tool to check for transmission-specific codes like P0971 (Pressure Control Solenoid 'A' Control Circuit High) or P2764 (Torque Converter Clutch Pressure Control Solenoid Control Circuit Low). These codes confirm the issue is in the transmission. A technician may also follow diagnostic procedures outlined in TSB 16-102-16R.
   Typical fix: Replacement of the entire CVT valve body assembly. Subaru has released updated valve bodies to improve durability. In some cases, a single solenoid can be replaced, 🎬 Watch: How to replace a single CVT solenoid but the full assembly is the more common and recommended repair. 🎬 Watch: Step-by-step CVT valve body replacement walkthrough
   Est. part cost: $800-$1500
2. Faulty ABS Control Module 🟡 Medium Probability → Shop ABS Control Module This is a more likely cause for the 2009 model or if no transmission codes are present on 2010-2014 models. Failures can be internal to the module or caused by water intrusion. A user on legacygt.com with a 2008 Legacy experienced multiple 'C' codes, including C0045, that pointed towards a faulty ABS module.
   How to confirm: After ruling out all other causes (wiring, other modules), the ABS module is the likely culprit. Diagnosis requires a high-end scan tool to attempt communication and check for internal fault codes. If a used module is installed, it may cause a C0045 code if not correctly programmed to the vehicle.
   Typical fix: Replacement and programming of the ABS control module. Sometimes the module can be repaired by a specialist.
   Est. part cost: $400-$1200
3. Wiring or Connector Issues ⚪ Low Probability Damage from previous accidents, corrosion, or rodent damage can disrupt the CAN bus wiring between the ABS, TCM, and ECM modules, causing communication faults. TSB 16-149-25 notes that condensation can seep into the transmission harness connector, causing various DTCs.
   How to confirm: Visually inspect the wiring harnesses going to the ABS module and transmission. Check for continuity and resistance on the CAN bus wires using a multimeter. TSB 16-102-16R recommends a 'wiggle-test' of harnesses while monitoring scan tool data to identify intermittent connections.
   Typical fix: Repairing the damaged section of the wiring harness or cleaning/replacing corroded connectors.
   Est. part cost: $10-$100

Rare But Worth Checking

• Incorrectly Programmed Replacement Module: If the ABS module was recently replaced with a used unit, it may have the incorrect programming (VIN) from the donor car, causing a communication fault. The EEPROM data may need to be cloned from the original module or programmed with a tool like the Subaru Select Monitor.

Diagnosis Steps

1. Connect a full-system scan tool capable of reading codes from all modules (Engine, Transmission, ABS).
2. Record all present codes. Do not clear them yet.
3. For 2010-2014 models: If any transmission codes (like P0971, P2764) are present, the transmission valve body is the primary suspect. Diagnose the transmission fault first.
4. Check for Subaru Technical Service Bulletin (TSB) 16-107-17R or others related to the CVT warranty extension to see if the repair is covered.
5. For all models: If no other codes are present, begin by inspecting the wiring and connectors to the ABS control module and transmission for any signs of corrosion, damage, or looseness. Perform a 'wiggle-test' on the harness while monitoring live data.
6. Follow the diagnostic flowchart in TSB 16-102-16R for a systematic electrical and component check if a related code like P0841 is present.
7. If wiring is intact and no other codes point to a different module, the fault is likely within the ABS control module itself.
8. Before replacing the ABS module, verify its power and ground connections are stable. Check for 10-15V at pin 28 and less than 0.5 Ω resistance to ground at pin 25 of the VDC/ABS module connector (B310).
9. If replacing the ABS module, ensure the replacement part is correctly programmed for the vehicle's VIN and options, as a used module may not work without reprogramming.

Parts You'll Likely Need

• CVT Valve Body Assembly (OEM #31705AA683 (This part number supersedes 31705AA620, 31705AA621, 31705AA682, and 31705AA690). Note: Always verify with VIN.) — This is the most frequent cause of C0045 on 2010-2014 Legacy models with the TR580 CVT.
  Trusted brands: Subaru (OEM)
  OEM price range: $1000-$1500
  Aftermarket price range: $600-$1000 (Remanufactured)
• ABS Control Module / VDC Hydraulic Unit — This is the likely failure point on 2009 models or on newer models where a transmission fault has been definitively ruled out.
  Trusted brands: Subaru (OEM), Bosch
  OEM price range: $1000-$1800
  Aftermarket price range: $300-$800 (Remanufactured/Repair Service)

Related Codes That Often Appear With This One

• P0971 — This transmission code for a pressure control solenoid circuit often accompanies C0045 on 2010-2014 models, pointing directly to the CVT valve body as the root cause.
• P2764 — Another common transmission code related to the torque converter clutch solenoid that confirms the problem originates in the CVT. A user on legacygt.com documented this code leading to a valve body replacement.
• C0057 — This code for 'ECM Control Malfunction' is a generic communication fault code that often appears alongside C0045, indicating a general network communication problem.

Technical Service Bulletins (TSBs) & Recalls

• 16-107-17R: Announces the CVT warranty extension to 10 years/100,000 miles for 2010-2015 Legacy/Outback and other models.
• 16-102-16R: Provides detailed diagnostic flowcharts for CVT-related DTCs like P0841 that can be associated with the C0045 sympathy code.
• 16-119-19: Announces a redesigned valve body to prevent false DTCs caused by aerated fluid.
• 12-197-16R: Pertains to the melting/sticky dashboard issue on 2005-2009 models, extending warranty coverage for a one-time replacement.
• 16-90-13R: Announces a countermeasure torque converter to address stalling/low RPM when stopping, caused by a worn thrust washer restricting lock-up clutch pressure release.

Platform-Specific Known Issues

• Subaru extended the warranty on the CVT assembly for many 2010-2015 models to 10 years / 100,000 miles, whichever comes first. This was announced in TSB 16-107-17R. Owners experiencing C0045 with related transmission codes should contact a Subaru dealer to check for warranty coverage, as the valve body replacement may be covered free of charge. For vehicles outside the 10yr/100k window at the time of the notice, a one-year extension was offered which ended July 31, 2018.

Mechanic-Grade Diagnostic Values

• TR580 CVT Lock-up Duty Solenoid Resistance — expected: 10 - 13.5 Ohms at 68°F (20°C).. Failure: A reading outside of this range, such as 2.5 Ohms or a very high (k-Ohm) reading, indicates a failed solenoid. The resistance should also be checked when hot, as failures can be temperature-dependent.
• TR580 CVT Other Solenoids Resistance — expected: The TR580 valve body contains multiple solenoids. Three typically have a resistance of 10-13.5 Ohms, while one has a resistance of 3-3.5 Ohms.. Failure: Any significant deviation from these values points to an internal solenoid failure.
• VDCCM&H/U (ABS Module) Power Supply Voltage — expected: 10 - 15 Volts. Failure: Voltage below 10V indicates a problem with the power supply circuit to the module.
• VDCCM&H/U (ABS Module) Ground Circuit Resistance — expected: Less than 0.5 Ohms. Failure: Resistance higher than 0.5 Ohms indicates a poor ground connection, which can cause communication faults.

Scan Tool Commands That Help

• Subaru Select Monitor (SSM) III/IV: Parameter Selection / Registration — This function is required after replacing the VDC (ABS) control module. It writes the vehicle's specific model information into the new module. Failure to perform this step will result in a 'Parameter selection failure' DTC and the C0045 code.
• Subaru Select Monitor (SSM) III/IV: Clear Memory — Used to erase stored DTCs from the ABS/VDC module after a repair is completed. This must be done after the 'Parameter Selection' function when a new module is installed.
• Subaru Select Monitor (SSM) III/IV: ABS Sequence Control Mode — This is a bidirectional test that activates the ABS hydraulic unit solenoids and pump in a specific sequence. It is used to verify the mechanical and electrical operation of the ABS pump and valves after ruling out communication issues.

Wiring & Ground Locations

• VDCCM&H/U Connector (B310) — On the ABS control module/hydraulic unit, located in the engine compartment.. This is the main connector for the ABS system. Pin 28 is the ignition power supply, and Pin 25 is the primary ground. These must be tested for correct voltage and resistance when diagnosing a communication fault.
• TCM Connector — On the Transmission Control Module. For the 2010-2014 Legacy, the valve body and its solenoids are located on the top of the transmission, accessible from the engine bay after removing the air intake assembly.. The connector on top of the transmission allows for testing the resistance of the internal CVT solenoids without removing the valve body. For example, the lock-up duty solenoid can be tested at pin 15.
• Data Link Connector (B40) — Located in the lower portion of the instrument panel on the driver's side.. This is the OBD-II port used to connect the scan tool. A diagnostic procedure for communication failure involves checking resistance between terminal 10 of this connector and chassis ground to verify the CAN bus integrity.

Real Owner Repair Stories

• Reddit user on r/subaru (2012 Impreza (uses TR580 CVT, same as Legacy)) — Dashboard lit up with codes P0700 (TCM Fault) and P2764 (Torque Converter Clutch Solenoid Circuit Low).
  ❌ Tried (didn't work) Replaced only the lock-up solenoid.
  ✅ What actually fixed it The single solenoid replacement worked for only one week before the codes returned. The user then concluded they needed to replace the entire valve body assembly to achieve a permanent fix.
• Reddit user on r/subaru (2014 Outback, 150k miles (uses TR580 CVT)) — Flashing brake and cruise control lights, check engine light on. Codes C0045 and C0042 (Low Voltage) appeared after a week of slow starting from a bad battery.
  ❌ Tried (didn't work) The user had the CVT valve body replaced 3 weeks prior to this incident for a separate solenoid issue.
  ✅ What actually fixed it Replacing the failing battery and clearing the codes resolved the issue. A forum expert noted that C0045 is a sympathy code for a TCM error, and C0042 is a low voltage code, both of which could have been triggered by the failing battery and may have been stored from before the valve body replacement.
• NHTSA ODI #10382746 (Platform Mate) — An owner reported that after shifting from Park to Back to Drive, a number of codes appeared including C0057, C0045, C0231, C0232, and C0282. The manufacturer advised the dealer to erase the codes and re-program the software.

OEM Part Supersession History

• 31825AA052, among others → 31825AA055 — Updated valve body design to improve reliability and address common solenoid failures.
  Heads up: A YouTube video creator noted that Subaru sells a kit under part number 31825AA055 which includes the new valve body, gasket, O-rings, and a protective plastic apron for installation.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Excessive Oil Consumption (FB Series Engines) 🔴 High — Common on 2013-2014 models with the 2.5L FB engine. A class-action lawsuit led to a settlement. (Ref: An extended warranty to 8 years/100,000 miles was provided as part of the lawsuit settlement for affected vehicles.)
• Lineartronic CVT Shudder and Failure 🔴 High — Widespread enough on 2010-2014 models to prompt a warranty extension. Issues include shuddering, stalling, and hesitation. (Ref: TSB 16-107-17R announced the CVT warranty extension to 10 years/100,000 miles.)
• Melting/Sticky Dashboard 🟠 Medium — Affects 2005-2009 Legacy models, where the dashboard material degrades in heat and humidity, becoming sticky or shiny. (Ref: TSB 12-197-16R extended the warranty for this issue to 10 years with unlimited mileage for a one-time replacement.)
• Prematurely Burnt-Out Headlights 🟡 Low — Commonly reported on 2010-2011 models, with owners stating bulbs fail in as little as six months.
• Head Gasket Failure 🔴 High — A well-known issue on pre-2012 Subaru models, typically occurring around 100,000 miles. It can lead to overheating and severe engine damage.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used OEM valve body from a low-mileage donor vehicle can be a cost-effective option, but it carries risks. It is most sensible when the budget does not allow for a new OEM or quality remanufactured unit. For the ABS module, a used part is viable but absolutely requires professional programming to the car's VIN.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a CVT Valve Body: Verify the donor vehicle's mileage and history if possible. Look for sellers who guarantee the part is tested and functional. Visually inspect the solenoids for the 'TOSOK' brand marking, which indicates it's an original OEM unit, as cheap aftermarket copies often lack markings.
• For an ABS Module: Ensure the part number matches exactly. Check for any physical damage, corrosion on the connectors, or signs that the electronic module has been separated from the hydraulic pump.
• Ask the seller for a warranty, even if it's only 30-90 days, to protect against receiving a dead-on-arrival part.

OEM-only on this vehicle (don't cheap out):

• CVT Valve Body Assembly: While some have had short-term success with single aftermarket solenoids (like Dorman), many forum and video reports indicate these often fail prematurely, leading to doing the job twice. The most reliable long-term repair is a new OEM valve body or a complete remanufactured OEM unit.

Aftermarket brands forum-validated for this vehicle:

• Dorman (for individual solenoid): Some owners report success, but others report premature failure. It is considered a budget-conscious but higher-risk repair compared to a full valve body replacement.

Brands owners have reported issues with on this vehicle:

• Unbranded, no-name valve bodies or solenoids from online marketplaces are a significant gamble. Many users report these parts failing within weeks or months.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0971 — Pressure Control Solenoid 'A' Control Circuit High; a transmission-specific code that often triggers C0045 as a sympathy code in the ABS module.
• P2764 — Torque Converter Clutch Pressure Control Solenoid Control Circuit Low; indicates a CVT solenoid failure that causes the TCM to send invalid data, resulting in C0045.
• P0841 — Transmission Fluid Pressure Sensor/Switch 'A' Circuit Range/Performance; a CVT-related DTC associated with C0045 diagnostics in TSB 16-102-16R.
• C0057 — VDC Control System/TCM Malfunction; frequently appears alongside C0045 when the root cause is a transmission internal fault.
• C0052 — Often found with C0045 on 2008-2009 models when the ABS control module has failed internally.
• C0071 — Steering Angle Sensor Malfunction; can appear as a companion code to C0045 during a total ABS module failure.

Frequently Asked Questions