DTC 115 — Engine Coolant Temperature Signal Out of Range – High — International DT466E

Navistar three-digit code for the DT466E indicating the ECM sees an ECT signal voltage above its valid range. The code is a sensor/circuit fault, not a true…

Updated October 15, 2026

What it means

DTC 115 is Engine Coolant Temperature Signal Out of Range – High on the International DT466E (1996–2003). Generic definition: ECT sensor signal voltage is above its valid range. On this platform the code typically points to an open ECT sensor, an unplugged/corroded connector or an open signal wire.¹

Most likely causes

1. Open ECT sensor element — The ECT thermistor is open internally, pulling the signal toward the high-voltage limit the ECM interprets as out-of-range high.¹
2. Unplugged or corroded ECT connector — Connector backed out or terminals corroded/oxidized at the sensor, creating high resistance or an open in the signal path.¹
3. Open or high-resistance signal wire between ECT and ECM — Chafed, broken or corroded wiring in the harness raises signal voltage seen by the ECM.¹

How to diagnose

1. Verify the code with a scan tool or flash code read; confirm DTC 115 is present and active.
2. Inspect the ECT sensor connector for being fully seated, corrosion, moisture or damaged terminals.
3. Check the ECT sensor resistance/voltage at the sensor connector with the harness disconnected; compare to expected values for temperature.
4. Inspect the ECT signal and reference wiring from the sensor back to the ECM for chafing, breaks, or corrosion; repair as needed.
5. Reconnect the sensor, clear codes, and recheck for DTC 115 to confirm the circuit is restored.

Parts and tools you may need

• Digital multimeter
• Navistar-compatible scan tool or flash code reader
• Contact cleaner and dielectric grease
• Replacement ECT sensor (if testing shows open)
• Basic hand tools for sensor access

Tools you’ll need

• Digital multimeter — Measures ECT sensor resistance and signal voltage to confirm an open/high circuit causing the out-of-range high reading.
• OBD-II scan tool — Reads and clears DTC 115 and monitors live ECT data to verify the fault is active and resolved after repairs.
• Terminal release tool set — Allows safe inspection and reseating of the ECT connector terminals to address corrosion or poor contact without damage.
• Inspection mirror and flashlight — Provides visibility of the ECT sensor and wiring harness in tight engine locations for chafing, breaks, or corrosion checks.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $140–$200 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If the code returns after sensor and connector service, or if wiring faults are found inside the main harness/ECM connector, have a qualified diesel technician trace the circuit and verify ECM inputs to avoid misdiagnosis.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources