ECU Unit for a 1993 SC 300 Manual 5-Speed

[Mr Toad]

I have a 1993 Lexus SC 300 that I have partially restored.  Mechanically, it is great.  The Speedometer is 10-15 MPH slower than actual speed.  The tachometer barely moves, the cruise control no longer responds.  I have searched online & don't expect to find a new ECU but I am not confident in any of the used choices out there.  Any suggestions on a reputable business that may have this?  Thank you

[RX400h06]

22 hours ago, Mr Toad said:

I have a 1993 Lexus SC 300 that I have partially restored.  Mechanically, it is great.  The Speedometer is 10-15 MPH slower than actual speed.  The tachometer barely moves, the cruise control no longer responds.  I have searched online & don't expect to find a new ECU but I am not confident in any of the used choices out there.  Any suggestions on a reputable business that may have this?  Thank you

CoPilot:

You're in good company, David—those early SCs are beautiful machines, and it sounds like you’ve done a solid job bringing yours back to life. The symptoms you're describing—erratic speedometer, weak tach, and dead cruise control—are classic signs of a failing ECU, especially due to capacitor leakage, which is common in these 30+ year-old units.

Here are two reputable ECU repair services that specialize in the SC300 and have strong track records:

🔧 Tanin Auto Electronix

• Service: Full ECU rebuild for 1992–1996 SC300/SC400
• What they do: Replace leaking capacitors, repair traces, clean the board, and test your ECU in an actual SC test vehicle.
• Why it stands out: They don’t just bench test—they plug your ECU into a real SC300 to verify idle, shifting, and CEL behavior.
• Cost: Starts at $199, with expedited options available
• More details on their ECU rebuild service

🛠️ Module Mechanics

• Service: ECU capacitor replacement and board repair for 1993–1997 SC300
• What they do: Replace leaking caps, attempt corrosion repair, and return your original unit.
• Note: They don’t test in-vehicle, so you’ll need to reinstall to verify success.
• Cost: Around $169.95, with optional expedited service
• Check out their SC300 ECU repair offering

If you’re leaning toward keeping your original ECU (which is smart for compatibility and VIN matching), you may want to contact Tanin Auto Electronix—they’re one of the few who actually test in a real SC chassis, which adds peace of mind.

[Mr Toad]

Thank you Dave!  I'll check them out