Toyota/Aisin Hybrid Direct Shift-CVT K120 Transmission / Driveline Family

Technical identity

Manufacturer group

Toyota/Aisin Hybrid

Transmission family

Direct Shift-CVT K120

Type

launch gear cvt

Speeds / ratio

CVT

Drivetrain layout

FWD

What to separate first in diagnosis

• Test electronic control, hydraulic pressure, clutch/converter and mechanical driveline behaviour separately.
• Temperature and fluid level/condition can directly affect pressure regulation and adaptation behaviour.
• Verify software, mechatronic and ratio variants within the same family by exact application/part identity.

Measurement sequence

1. Confirm exact transmission code and software/application variant.
2. Verify fluid level, condition and temperature.
3. Capture input/output speeds and actual ratio.
4. Test electronic command, hydraulic pressure and mechanical clutch separately.
5. Verify shift/adaptation result under load.

Driveline live-data package

• Freeze frame: first/last fault time, RPM, load, vehicle speed, system voltage, core temperatures and companion DTCs.
• Electrified layer: SOC/SOH where available, cell delta, pack temperatures, HVIL/isolation, contactor permission, DC-DC output and 12 V voltage.
• Driveline: input/output speeds, commanded/actual ratio, clutch/TCC slip, fluid temperature, actuator/solenoid command and adaptations.

Driveline measurement chain

1. 1) Match vehicle/generation/market/powertrain/driveline identity to the source record; family name alone is not fitment evidence.
2. 2) Preserve freeze frame and companion DTCs before clearing; make the first-fault condition reproducible.
3. 3) Verify power/ground and network communication under load; do not decide from key-on static measurement alone.
4. 5) Compare electronic command → hydraulic/actuator response → mechanical slip/ratio result at the same temperature and load.
5. 6) After repair, recreate the same load/temperature and verify DTC state, live-data deviation and user symptom together.

Fluid type/level temperature, pressure thresholds, adaptation limits and part codes are not asserted without application-specific OEM evidence.

Driveline root-cause split

• For READY/charging faults, separate 12 V supply from the HV permission chain first; low 12 V can mimic contactor/HVIL/isolation faults.
• For battery performance, use cell delta, temperature spread and voltage deviation under load/charge instead of one SoH percentage alone.
• For CVT ratio faults, identify the architecture first; e-CVT motor-generator power split and belt/chain CVT hydraulic-pulley faults do not share the same diagnostic tree.