Engine Ambient Air Temperature Sensor 1
Indicates a fault with the engine ambient air temperature sensor.
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 engine is trying to measure the air temperature around it but is getting a weird reading, meaning the sensor might be faulty.
What the computer is actually seeing
The Engine Control Module (ECM) expects a voltage between 0.5V (cold) and 4.5V (hot) from the ambient air temperature sensor. If the voltage is out of this range, it triggers this code.
What a healthy reading looks like
0.5V to 4.5V for normal operation based on ambient temperature.
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.
- 1Check the ambient air temperature sensor connector and wiring for damage or corrosion - repair if found.
- 2Verify the sensor operation by measuring its voltage output; it should vary between 0.5V and 4.5V based on the air temperature.
- 3If the voltage is outside this range, replace the ambient air temperature sensor.
Common causes
- Faulty ambient air temperature sensor
- Wiring issues or poor connections to the sensor
- Open circuit or short in the sensor circuit
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but it's best to fix soon as it can affect engine performance and fuel efficiency.
Will this code come back after clearing?
If the issue persists, the code will likely return after clearing.
Why do I see SPN 734 with other temperature codes?
Temperature sensors can fail or short out together, leading to multiple codes showing similar faults.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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