U660E Solenoid Kit 2018-2020

This U660E solenoid kit is listed for the 2018-2020 Lexus NX300 and comes as an assembly: the full solenoid set already connected to the internal wiring harness and its case pass-through connector, as shown in the photo. That matters on a late-model U660E, because a heat-hardened harness or a leaking pass-through connector produces the same erratic shifts and solenoid codes as a worn solenoid. Replacing the solenoids and harness together removes both causes at once.

What the solenoid and harness assembly does in a U660E

The U660E is the Aisin six-speed front-drive transaxle Toyota and Lexus have used since the 2007 ES350 and Camry. The NX300 pairs a version of it with the 2.0L turbo four. The computer controls every shift through linear solenoids, which regulate line pressure, lockup and the clutch apply and release, and one on/off solenoid that positions a shift valve. Each solenoid plugs into the internal harness, and the harness carries every signal through a single connector in the case. Under the pan, that harness lives in hot fluid for its entire life, which is why the insulation and connector seals on older units become brittle.

Symptoms this kit addresses

• Erratic or skipped shifts, or a shift that happens too early or too late
• Limp mode with a fixed gear and a warning light
• Solenoid electrical codes that come and go, often from a harness or connector fault
• Pressure control solenoid performance codes such as P0746, P0776, P0796 or P2714
• Harsh engagement into Drive or Reverse and shudder during light-throttle lockup
• Fluid weeping from the case connector area

How to confirm the fault

Separate electrical from hydraulic causes first. An intermittent electrical code that changes when you wiggle the connector at the case points to the harness. A performance code with good electrical readings points to a sticking solenoid, worn valve body bores or fluid problems. Set the fluid level hot (185-194°F) through the overflow plug with Toyota WS ATF, address any engine fault, and use Check Mode so codes set quickly on a road test. Our U660E and U760E problems guide covers these steps and the shudder test, and our U660E fluid type and capacity guide covers the fill.

Fitment

This listing is for the U660E in 2018-2020 vehicles, with the Lexus NX300 named as the application. Other U660E vehicles from earlier years use similar solenoids, but harness routing and connectors can differ between models, and AWD versions may use the U660F or a related transaxle. Do not assume a fit from the transmission family alone. Compare the harness routing, connector style and solenoid count against the photo, read the code on the case, or send us your year and VIN to confirm. Other U660E solenoid kits, including versions without the harness, are on our U660E/U760E collection page.

Install notes

• Drain the fluid and remove the pan and strainer; release the case connector retainer before unbolting the harness and solenoids.
• Replace the pass-through connector O-ring and lubricate every solenoid O-ring with WS fluid so nothing is cut during installation.
• Route the harness exactly as the original and secure it in every clip so it cannot contact the pan or moving parts.
• If the valve body bores are worn, new solenoids will not cure flare or shudder; a U660E valve body is the next step.
• Refill with Toyota WS ATF (00289-ATFWS), set the level hot, clear codes and reset the learned values with a capable scan tool.

If the pan shows heavy clutch material, a complete overhaul makes more sense; we carry a U660F master rebuild kit and other overhaul kits for this family.

Does this kit include the wiring harness?

Yes. It is pictured as the full solenoid set connected to the internal wiring harness with its case connector.

Will it fit a 2016 NX200t?

The listing is for 2018-2020 vehicles named as the NX300. NX200t models are similar, but send your VIN so we can confirm the harness and connectors match before you order.

Do I need to replace the harness if only one solenoid code is set?

Not always, but if the harness is brittle, the connector leaks or the codes are intermittent, replacing the harness with the solenoids avoids a second repair.

What fluid does the U660E take?

Toyota WS ATF, part 00289-ATFWS. Check the level hot at 185-194 degrees F through the overflow plug.

Is a relearn required?

Yes. Clear codes and reset the ECT learned values with a scan tool that supports it, then drive from cold to operating temperature.

• Toyota/Aisin U660E and U760E: Shudder, Valve Body Wear, and the WS Fluid-Level Procedure
• U660E Fluid Type, Capacity and Service Interval