Temperature Sensor 1 Circuit Low
The temperature sensor circuit voltage is too low indicating a potential fault.
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What it means (plain English)
The ECM is getting a lower voltage from the temperature sensor than expected, which usually means there's a problem with the sensor or its wiring.
What the computer is actually seeing
The Engine Control Module (ECM) expects to see a voltage signal from the temperature sensor between 0.5V and 4.5V corresponding to the temperature readings. A signal below 0.5V is considered out of range and triggers this code.
What a healthy reading looks like
Voltage from the sensor should be between 0.5V (high temp) and 4.5V (low temp) with typical readings depending on actual 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 wiring and connectors for damage or corrosion, repair as necessary. Decision: Proceed if no visible issues; if issues found, fix them and retest.
- 2Measure the voltage at the temperature sensor connector with the key on, engine off. Expected value: should be about 0.5V to 4.5V. Decision: If proper voltage, suspect ECM; if voltage is low, proceed to next step.
- 3Disconnect the temperature sensor and measure the resistance across the sensor terminals. At normal temp (say 20°C or 68°F), resistance should be around 2.5k ohms. Decision: If resistance is off, replace the sensor; if not, check the ECM. Confirm no damage before proceeding.
Common causes
- Faulty temperature sensor
- Wiring issues (shorts or opens)
- Connector corrosion or poor connection
- ECM issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's safe to drive, but expect possible engine performance issues. Fix it soon.
Will this issue come back after repair?
If all components were correctly diagnosed and repaired, it shouldn't come back.
Why does this code appear with SPN 1600?
SPN 1600 is often related to the overall function of the temperature sensor circuit; they can trigger simultaneously if there's a common fault.
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