Parts for your 2019 Toyota Mark x-Tx valve

2019 Toyota Mark X TX valve: what it does, where it lives, and how to look after it

Short answer: the 2019 Toyota Mark X does use a TX valve (thermostatic expansion valve). This is confirmed by Toyota’s Electronic Parts Catalog for GRX130/133-series Mark X (Air Conditioning – Cooler Unit diagrams listing the “Cooler Expansion Valve”), Toyota repair manual A/C sections for the model family, and DENSO HVAC technical literature that specifies TXV-type metering on contemporary Toyota passenger vehicles.

On this car, the TX valve meters liquid refrigerant into the evaporator, balancing inlet pressure and evaporator outlet temperature to keep superheat in the sweet spot. That means stable cabin temps, strong cooling at idle, and good compressor protection. When it’s doing its job, you get quick pull-down on a hot day and even, consistent air out of the vents.

There’s no scheduled service interval for the TX valve, it’s a replace-on-condition part. Still, a few habits help it live a long, drama-free life:

• Run the A/C regularly to keep seals lubricated and moisture at bay.
• Keep the condenser clean and the cabin filter fresh so airflow and pressures stay in range.
• If the system is opened, always replace O‑rings and the receiver/drier, evacuate thoroughly, and recharge by weight to the under‑bonnet spec.

Typical signs a Mark X TX valve is on the way out include weak or intermittent cooling, frosting at the evaporator or lines, hissing and hunting vents temps, or odd high/low gauge readings. Contamination after a compressor issue can also stick the valve. The A/C amplifier may log related DTCs if pressures go out of whack.

Location-wise, the TX valve is mounted at the evaporator inlet, inside the HVAC box behind the glovebox area. Replacing it generally involves recovering the refrigerant, removing glovebox/trim to access the cooler unit, disconnecting the engine‑bay lines at the firewall, swapping the valve and O‑rings, evacuating to deep vacuum, then recharging with the specified refrigerant and correct PAG oil balance. It’s a tidy job for a licensed tech, in Australia and New Zealand, refrigerant handling must be done by certified professionals (e.g., ARCtick in AU).

Done right, a fresh TX valve restores crisp, reliable cooling and protects the rest of the system—particularly handy when summer turns the cabin into an oven.

Technical sources referenced (no external links provided):

• Toyota Electronic Parts Catalog (GRX130/133) – Air Conditioning/Cooler Unit: “Cooler Expansion Valve” listing
• Toyota Repair Manual for Mark X platform – A/C system sections illustrating TXV at the evaporator
• DENSO HVAC technical literature on TXV-based metering in Toyota passenger vehicles

FAQs

Does the 2019 Toyota Mark X use a TX valve or an orifice tube?
It uses a thermostatic expansion valve. Toyota’s parts and service documents for the GRX130/133 Mark X list a “Cooler Expansion Valve” at the evaporator, which is the TXV. An orifice tube isn’t used on this model.

Where is the TX valve located, and how hard is it to replace?
It’s mounted at the evaporator inlet inside the HVAC unit behind the glovebox. Replacement typically needs refrigerant recovery, glovebox/trim removal, disconnecting the lines at the firewall, swapping the valve with new O‑rings, then vacuum and precise recharge. Best left to an authorised A/C technician due to legal and safety requirements.

What are the symptoms of a failing TX valve on a Mark X?
Fluctuating vent temperatures, poor cooling at idle but better at speed, frosting on the evaporator/lines, unusual hissing, and abnormal high/low side pressures. After compressor failures, debris can stick the TXV, causing similar issues.