Intake Air Temperature Sensor 1 Circuit High
Intake air temperature sensor circuit voltage is too high.
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What it means (plain English)
The engine's computer monitors the intake air temperature to adjust fuel and timing, but it's detecting a higher voltage than normal from the temperature sensor, meaning the sensor may be faulty or wired incorrectly.
What the computer is actually seeing
The engine control module (ECM) expects a voltage signal between 0.5V to 4.5V from the intake air temperature sensor based on temperature variations. If the voltage exceeds 4.5V, it triggers the fault code SPN 1659.
What a healthy reading looks like
Normal operation should see intake air temperature between about 10°C (50°F) to 70°C (158°F) translating to 1V to 2.7V output if using a typical 0.5V to 4.5V output range.
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. Visually inspect the intake air temperature sensor and connector for damage or corrosion. - If damaged, repair or replace as necessary.
- 22. Measure the voltage at the intake air temperature sensor connector with the key on and the engine off. It should be between 0.5V and 4.5V. - If voltage is above 4.5V, check for short to power; repair wiring as needed.
- 33. If the voltage is normal, check the resistance of the intake air temperature sensor at various temperatures. - If resistance is out of spec, replace the sensor.
- 44. If all tests pass, consider a reprogram or replacement of the ECM.
Common causes
- Faulty intake air temperature sensor
- Corroded or damaged wiring
- Bad connectors
- ECM malfunction
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It may be drivable but expect poor engine performance and fuel economy, so fix soon.
Will this code come back after clearing it?
If the underlying issue isn't fixed, it will likely return.
Why does this code pair with others like SPN 1658?
They often relate to intake air temperature problems, indicating a possible sensor failure or circuit issues.
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