DTC 322 — Engine Coolant Temperature Above Critical Level — International DT466E

Diagnostic guide for International DT466E (1996–2003) Navistar three-digit code 322.

Updated October 15, 2026

What it means

Engine coolant temperature is above the critical level. On the DT466E the ECM can warn, derate or shut down for high coolant temperature (321/322) depending on programming.¹²

Most likely causes

1. Low coolant level or loss of coolant — Low coolant reduces heat transfer and can trigger critical temperature. Check level, look for external leaks, and verify coolant level sensor operation. DTC 323 covers low coolant level on this platform.¹³
2. Insufficient radiator airflow / cooling fan not engaging — A stuck or inoperative fan clutch, missing fan drive, or blocked airflow raises coolant temperature. Verify fan operation and radiator condition.¹²
3. Restricted coolant flow — A stuck thermostat, plugged radiator, or collapsed hose limits circulation. Typical causes for high temperature codes on this platform include a stuck thermostat and a plugged radiator.¹²
4. ECT sensor or circuit fault causing false high reading — An open or corroded ECT sensor/connector or wiring fault can drive the signal high. DTC 115 is ECT signal out of range high on this platform.⁴

How to diagnose

1. Confirm active code 322 with a scan tool or flash code read; DTC 111 means no faults.
2. Inspect coolant level in the recovery tank and radiator (engine cold). Look for leaks, low level, or signs of coolant loss.
3. Check radiator for external blockage, debris, and verify airflow through the core.
4. Verify cooling fan engagement and fan clutch operation under load; listen/observe fan speed increase when temperature rises.
5. Inspect thermostat operation and radiator flow; check for overheating symptoms and coolant circulation.
6. Inspect ECT sensor connector for corrosion or looseness and check wiring integrity; compare ECT reading to a known-good thermometer if available.
7. If temperature is truly high, stop and let the engine cool; the engine may be programmed to shut down on critical temperature.

Parts and tools you may need

• Scan tool capable of Navistar three-digit flash codes
• Infrared thermometer
• Mechanical coolant pressure tester
• Coolant hydrometer/refractometer
• Basic hand tools for fan clutch and thermostat inspection

Tools you’ll need

• OBD-II scan tool — Reads active DTC 322 and live ECT data to confirm a real over-temperature versus a sensor fault.
• Digital multimeter — Checks ECT sensor resistance/voltage and wiring integrity to rule out a false high reading.
• Infrared thermometer — Verifies actual coolant temperature at the thermostat housing/radiator to compare with ECM-reported ECT.
• Cooling system pressure tester — Detects coolant loss/leaks and confirms proper system pressure that affects boiling point and flow.

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 engine shuts down on protection, shows signs of severe overheating (steam, coolant loss, warped components), or if ECT readings do not match actual temperature after sensor/wiring checks, have the cooling system professionally evaluated. Do not continue operation with critical over-temperature.

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