Engine Overtemp Condition
Your engine is running hotter than it should be, like a car left in the sun with no airflow. The ECU detected coolant temperature exceeding safe limits and triggered this warning to prevent engine damage.
The ECM monitors coolant temperature via the engine coolant temperature (ECT) sensor and compares it against programmed thresholds. When coolant temp exceeds the maximum safe operating temperature (typically 115-125°C), the ECU sets this fault code to protect the engine from thermal damage.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Coolant Temperature | 80–105°C (176–221°F) | >115°C (>239°F) |
| ECT Sensor Signal | 0.5–4.5V (linear with temp) | Voltage indicating >115°C |
Code P0218 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0218 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.