Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer has detected a problem with the system that controls the engine's temperature, and it's asking to turn on the check engine light.
The P25AF code indicates a request from the coolant temperature control module to illuminate the malfunction indicator lamp (MIL) due to a detected issue.
The coolant temperature control module is responsible for managing the engine's operating temperature. It communicates with the vehicle's main computer (ECU) to ensure optimal temperature is maintained. If it detects an issue that could affect performance or emissions, it requests the MIL to alert the driver.
• Check engine light is on
• Engine overheating
• Poor fuel economy
• Faulty coolant temperature control module
• Wiring issues or poor connections
• Malfunctioning temperature sensors
MIL: Malfunction Indicator Lamp
ECU: Engine Control Unit
• Use an OBD-II scanner to confirm the code
• Inspect the wiring and connectors for damage
• Test the coolant temperature control module
• Replace faulty coolant temperature control module
• Repair or replace damaged wiring
• Replace malfunctioning temperature sensors
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $500
Moderate
• Vehicle 1
• Vehicle 2
• Vehicle 3
• Regular maintenance of cooling system
• Check coolant levels frequently
• Inspect wiring and connectors periodically
Sensor Issue
• Do not ignore the check engine light
• Have the vehicle inspected by a professional
• Avoid driving the vehicle if overheating occurs
Check with your vehicle manufacturer for specific warranty coverage related to the cooling system components.
This code has been associated with issues in vehicles with advanced cooling systems that use electronic control modules.
Moderate – Addressing this issue is important to prevent engine damage.
Driving with an illuminated check engine light can lead to further damage and may not comply with emissions regulations.
• Engine at operating temperature
• Vehicle stationary
The coolant temperature control module is typically located near the engine, often integrated with the thermostat housing or radiator.
Q: Can I drive with a P25AF code?
A: It's not recommended to drive with this code, as it may indicate a risk of engine overheating.
Q: How can I reset the check engine light?
A: You can reset the light using an OBD-II scanner after addressing the underlying issue.
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Universal · Digital multimeter
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Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Relevant when coolant-temperature and warm-up faults indicate a thermostat-related issue.
Coolant-temperature and warm-up faults often lead to thermostat testing and replacement.
Thermostats are vehicle-specific and should be matched by engine and housing style.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.