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.
Control After Start
After engine start, ECM turns ON the coolant pump Switchover valve to turn OFF the coolant pump. This stops the coolant circulation.
ECM controls the coolant Switchover valve to adjust negative pressure on the vacuum actuator
installed to the coolant pump. Via the vacuum actuator rod, ball rotary valve
is closed allowing the coolant flow to be stopped. This stops coolant to flow to the cylinder head.
| Belt pulley | |
| Coolant pump housing |
When all of the following conditions are satisfied, ECM performs the cold start control to deactivate the coolant pump.
- Engine coolant temperature: 85°C (185°F) or less
- Charge air temperature: below threshold limit
- Engine speeds: 4000 RPM or less
- No heater request from A/C auto amp.
When coolant pump stop conditions are not satisfied, ECM turns OFF the coolant pump Switchover valve. Negative pressure on the coolant pump Switchover valve is ventilated through the air vent. The spring force returns the ball rotary valve in the direction flowing coolant. This turns ON the coolant pump, allowing coolant circulation again.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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