Evaporator Temperature Sensor Voltage Low
Indicates the evaporator temperature sensor voltage is below the expected range.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The evaporator temperature sensor tells the computer how cold the air coming from the AC evaporator is. If it's sending a very low voltage signal (like under 0.5 volts when it should be closer to 1.5-4.5 volts), it means the sensor may be faulty or there could be a wiring issue.
What the computer is actually seeing
The computer monitors the voltage from the evaporator temperature sensor, which should range from 1.5 to 4.5 volts. If it detects a voltage below 0.5 volts, it triggers the code SPN 1504.
What a healthy reading looks like
1.5 to 4.5 volts from the evaporator temperature sensor under normal operation conditions.
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 the wiring and connector for the evaporator temperature sensor for any signs of damage or corrosion. Repair as necessary. Decision: If fixed, clear the code and retest.
Common causes
- Faulty evaporator temperature sensor
- Damaged or corroded wiring
- Loose or disconnected connector
- Short to ground in the sensor circuit
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, the vehicle is drivable but the AC performance may be affected.
Will this code come back after I clear it?
If the underlying issue isn't fixed (like a bad sensor), yes, it will return.
Why does this code pair with SPN 1503?
SPN 1503 indicates high voltage from the same sensor; both codes point to sensor problems.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →