Engine Coolant Temperature (ECT) Sensor Low Voltage
The engine coolant temperature sensor is reporting a voltage lower than expected.
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What it means (plain English)
The ECT sensor measures how hot the coolant is. If it shows a low voltage, the computer thinks the coolant is much cooler than it actually is, which can lead to poor performance or overheating.
What the computer is actually seeing
The engine computer expects the ECT sensor to send a voltage between 0.5V to 4.5V based on coolant temperature. If it sees a voltage under 0.5V, it triggers this fault code.
What a healthy reading looks like
Normal operating coolant temperatures should show about 1.0V (for ~32°F) up to 4.0V (for ~248°F). Voltage under 0.5V indicates a problem.
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 to the ECT sensor for damage or corrosion. Repair as needed.
- 2Measure the voltage at the ECT sensor connector with the ignition on (engine off). Expected should be between 0.5V and 4.5V. If low, proceed to step 3.
- 3Test the ECT sensor by disconnecting it and measuring resistance across its terminals. You should see between 500 ohms (at 176°F) to 3.3k ohms (at 32°F). If out of range, replace the sensor.
- 4If the sensor tests good, inspect the wiring between the sensor and the ECM. Look for shorts or opens. Repair or replace as needed. If all looks good, check the ECM for faults.
Common causes
- Open or short in the ECT sensor circuit
- Faulty ECT sensor
- Wiring damage or poor connections
- Corroded connectors
- Temperature misread due to engine issues
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Not recommended. Poor coolant reading can cause engine overheating or poor performance.
Will this code come back after clearing?
It can if the underlying issue isn't resolved, especially if the sensor or wiring is faulty.
Why does this code pair with SPN 460?
SPN 460 also indicates ECT-related issues, often occurring from similar wiring or sensor faults.
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