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Subaru Brz Automatic Transmission Torque Converter Inhibitor Relays

Subaru Brz Automatic transmission torque converter inhibitor relays

Starting at low prices, AutoBuffy stocks multiple automatic transmission torque converter inhibitor relays from top OE-quality brands. This relay controls whether the torque converter clutch can engage by acting as an electrical gatekeeper in the TCC circuit. When it fails, the transmission may lose lockup function entirely, hurting fuel economy and potentially damaging the converter over time.

Signs your Subaru Brz needs a new automatic transmission torque converter inhibitor relay

  • Torque converter clutch never engages, causing the engine to rev higher than normal at highway speeds
  • Noticeable drop in fuel economy on steady highway driving where lockup should hold
  • Transmission control module stores TCC-related fault codes such as P0740, P0743, or P0748
  • Transmission shifts correctly through all gears but feels loose or slips slightly at cruising speed
  • Check Engine or Transmission warning light illuminates, specifically after extended highway operation
  • Relay clicks or chatters audibly in the fuse/relay box, or shows no response at all when tested with a multimeter

Which automatic transmission torque converter inhibitor relay should you buy for your Subaru Brz?

The inhibitor relay for the TCC circuit is a small but safety-critical component, and fitment precision matters more than brand prestige here. Your main decisions are whether to buy an OEM-equivalent relay or a higher-grade unit, and whether your Subaru Brz requires a sealed weatherproof version or a standard open-frame relay. Always confirm the relay's coil voltage rating, pin count, and terminal layout match the original before purchasing.

OEM-Equivalent Replacement
Best for
Restoring factory TCC behavior on a daily driver
What you get
Direct plug-and-play fitment, matched coil resistance, and reliable re-engagement of lockup function
Heavy-Duty / High-Cycle Relay
Best for
High-mileage vehicles or those used for towing and frequent stop-and-go driving
What you get
Reinforced contact points rated for more switching cycles, reducing the chance of early repeat failure
Weatherproof / Sealed Relay
Best for
Subaru Brz applications where the relay mounts in an exposed or underhood location near heat and moisture
What you get
Sealed housing that resists corrosion and vibration, extending service life in harsh environments
OEM Dealer Part
Best for
Vehicles still under powertrain warranty or where exact part numbers are required by the manufacturer
What you get
Factory specification guaranteed, but typically higher cost with no performance advantage over quality OEM-equivalent units

Replacing the automatic transmission torque converter inhibitor relay on a Subaru Brz

Easy⏱ 15–30 minutesRelay puller or small flathead screwdriverMultimeterOBD-II scan toolFuse block cover removal tool or trim pry tool

Locate the relay in the underhood or interior fuse and relay block using your Subaru Brz owner's manual or fuse diagram, then pull the old relay straight out and press the new one firmly into the same socket until it seats fully. After installation, use a scan tool to clear any stored TCC fault codes and perform a short highway drive to confirm the torque converter clutch engages and holds at cruising speed. No special calibration is required — the relay is a direct mechanical swap.

Frequently asked questions

How much does it cost to replace automatic transmission torque converter inhibitor relays on a Subaru Brz?
The part itself starts at low prices and is one of the more affordable transmission electrical components. Labor is minimal since the relay typically swaps in seconds at the fuse block. Total repair cost — parts and shop labor combined — usually stays well below the cost of diagnosing and replacing the torque converter itself if lockup failure is left unaddressed.
What does the torque converter inhibitor relay actually do in my Subaru Brz?
The relay acts as an electrically controlled switch in the torque converter clutch circuit. When the transmission control module signals that conditions are right for lockup — typically steady highway speed and proper fluid temperature — it energizes the relay, which then allows current to flow to the TCC solenoid. Without a working relay, that signal never reaches the solenoid.
Can I drive my Subaru Brz with a failed torque converter inhibitor relay?
Yes, but only in the short term. A failed relay typically prevents TCC lockup rather than causing full transmission failure, so the vehicle will still move and shift. However, the open converter clutch generates heat and reduces fuel economy. Extended driving in this condition accelerates fluid degradation and can cause broader torque converter damage that is far more expensive to repair.
How do I test a torque converter inhibitor relay on my Subaru Brz before replacing it?
Remove the relay from the fuse block and test it with a multimeter. Check coil resistance across the control terminals — an open circuit or reading far outside spec indicates a failed coil. Then apply 12V to the control terminals and use the multimeter to confirm the load-side contacts close. A relay that does not click or conduct when energized should be replaced.
Will replacing the torque converter inhibitor relay clear the TCC fault codes on my Subaru Brz?
Replacing the relay resolves the fault only if the relay was the root cause. After installation, clear stored codes with a scan tool and drive at highway speed to run the TCC monitor. If the code does not return and lockup engages normally, the relay was the problem. Returning codes point to a faulty TCC solenoid, wiring issue, or TCM problem instead.
Is the torque converter inhibitor relay the same as the TCC solenoid on my Subaru Brz?
No, they are separate components. The TCC solenoid is a hydraulic valve mounted inside the transmission valve body that physically applies and releases the converter clutch. The inhibitor relay is an external electrical relay that controls whether power reaches that solenoid. Both can cause identical TCC fault codes, so testing each component individually is the correct diagnostic approach.

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