Engine Coolant Temperature Sensor 2 - Voltage Above Normal
Indicates that the engine coolant temperature sensor 2 has a high voltage reading.
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What it means (plain English)
The coolant temperature sensor 2 is measuring a voltage higher than it should be, which usually indicates a fault in the sensor or its circuit. Normal operation should show around 0.5V to 4.5V depending on the coolant temperature.
What the computer is actually seeing
The engine control module (ECM) monitors the voltage from coolant temperature sensor 2. If the voltage goes above a specific threshold (typically over 4.5V), it triggers the SPN 3915 fault code.
What a healthy reading looks like
Expected voltage from the sensor should range from 0.5V (cold) to 4.5V (hot).
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect wiring and connectors related to the coolant temperature sensor 2 for damage or corrosion. If found, repair/replace as needed.
- 22. With the engine at operating temperature, use a multimeter to measure the voltage at the coolant temperature sensor 2 connector. If the voltage is above 4.5V, proceed to step 3. If it's within range, consider the sensor may be faulty or the ECM may be at fault.
- 33. Disconnect the sensor and measure the resistance across the sensor terminals. The resistance should change with temperature (around 2.5k ohms at 25°C). If the readings are unusual, replace the sensor.
- 44. If the sensor is fine, inspect the wiring harness back to the ECM for continuity. If there's an open circuit or short, repair the wiring accordingly.
Common causes
- Short circuit in the wiring to the coolant temperature sensor
- Faulty coolant temperature sensor 2
- Corroded or loose connector at the sensor
- Open circuit in the wiring to the sensor
Typical repair cost
$$
Related codes
Frequently asked questions
Can I continue to drive with this code?
It's better to fix it soon, as it can lead to overheating if the ECM can't get accurate coolant temperature readings.
Will this code come back after I clear it?
If the underlying cause isn’t fixed, yes, it will likely return.
Why do I see this code with other SPNs?
Often, if the temperature sensor fails, it can trigger related codes for other sensors that depend on accurate temperature readings.
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