MID 146 - Temperature Sensor 1
The ECM is detecting an issue with Temperature Sensor 1.
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What it means (plain English)
The Engine Control Module (ECM) relies on Temperature Sensor 1 to monitor coolant temperature. If this sensor fails or gives wrong readings, the engine can't properly manage performance and emissions.
What the computer is actually seeing
The ECM expects a voltage output between 0.5V to 4.5V from the sensor, corresponding to coolant temperatures of approximately -40°C to +125°C (-40°F to +257°F).
What a healthy reading looks like
Expected voltages from the temperature sensor should be a smooth range between 0.5V (cold) and about 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. Check the wiring and connectors for the temperature sensor for damage or corrosion. Repair if necessary.
- 22. Measure the voltage at the sensor connector while the engine is running. It should vary between 0.5V and 4.5V. If it’s stuck or out of range, go to step 3.
- 33. Unplug the sensor and measure the resistance. Compare the reading to manufacturer specs (typically around 1k ohm at 25°C). If it's out of spec, replace the sensor.
- 44. If the sensor is good, check the ECM for software updates or faults. Ensure there are no other related fault codes. Clear and retest for codes. If the code returns, the ECM may need to be replaced.
Common causes
- Faulty temperature sensor
- Damaged wiring or connectors
- Corrosion at the connector
- ECM calibration issues
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's best to fix this soon to avoid engine performance issues, but it's generally drivable for a limited time.
Will this problem come back after repair?
If the root cause (bad wiring or connectors) is fixed, the problem should not return.
Why does this code accompany other sensor codes?
Intermittent faults or common wiring issues often cause multiple sensor codes to appear.
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