Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Temperature Control Switch (ECHO)
On vehicles equipped for cold areas, temperature control switch operates a maximum hot switch which provides an input signal to Engine Control Module (ECM) for controlling Positive Temperature Coefficient (PTC) heater. PTC heater is a small electrical heater located in the heater core. Maximum hot switch may also be referred to as MAX HOT switch. For additional information on PTC heater, see POSITIVE TEMPERATURE COEFFICIENT (PTC) HEATER under MISCELLANEOUS CONTROLS.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.