Temperature Sensor 1 (High Side)
This code indicates a high temperature reading from Engine Coolant Temperature (ECT) sensor 1.
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's coolant temperature sensor is reading a higher temperature than expected, which can lead to overheating if not addressed.
What the computer is actually seeing
The engine control module (ECM) reads a voltage signal from the temperature sensor, correlating to coolant temperature between 0-5 volts. A reading above the expected threshold indicates an issue.
What a healthy reading looks like
Normal coolant operating temperature should range from 180°F to 220°F (82°C to 104°C). A signal greater than 4.5 volts may trigger this code.
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 engine coolant level; ensure it's within the normal operating range before proceeding.
- 22. Inspect the wiring and connectors to the engine coolant temperature sensor for damage or corrosion.
- 33. Use a multimeter to measure the voltage at the ECT sensor connector; compare readings to expected values (0-5V).
- 44. If voltage is above 4.5V, replace the engine coolant temperature sensor. If normal, proceed to check for ECM faults.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues, such as shorts or opens in the sensor circuit
- Low coolant level affecting temperature readings
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with SPN 48 active?
It's moderate severity. Drive cautiously and fix soon to avoid overheating.
Will this code come back after clearing?
If the underlying issue isn't resolved, it likely will return.
Why does this code pair with SPN 49 or SPN 50?
These codes relate to related sensors or systems that monitor the same conditions or may be affected by the same faults.
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