DTC 311 — Engine Oil Temperature Signal Out of Range – Low — International DT466E

Navistar three-digit DTC 311 on International DT466E (1996–2003) indicates the engine oil temperature sensor signal is below the valid range. The code is a…

Updated October 15, 2026

What it means

DTC 311 is the Navistar code for Engine Oil Temperature Signal Out of Range – Low. The ECM sees the EOT sensor signal voltage below its valid range. On the DT466E this is typically a shorted EOT sensor or the signal wire shorted to ground; EOT affects cold-start and injection control.¹

Most likely causes

1. Shorted EOT sensor internally pulling signal to ground — A failed thermistor inside the EOT sensor can short the signal to ground, producing a low voltage reading. This is the common failure mode for a low-range EOT fault on the DT466E.¹
2. EOT signal wire shorted to chassis/engine ground — Chafed or pinched wiring between the sensor and ECM can contact ground, forcing the signal low. Inspect harness routing near hot or moving parts.¹
3. Corroded or contaminated EOT connector causing a low-resistance path to ground — Moisture or oil intrusion at the sensor connector can create a leakage path to ground, biasing the signal low.¹
4. ECM reference/return circuit issue affecting the EOT input — A problem with the 5 V reference or sensor ground shared with other sensors can pull the EOT input low. Compare with other sensor codes if present.¹

How to diagnose

1. Verify the code with a scan tool and note freeze-frame conditions; clear and retest to confirm repeatability.
2. Inspect the EOT sensor connector for corrosion, oil intrusion, or loose terminals; repair as needed.
3. Perform a visual and tactile inspection of the EOT signal wiring from sensor to ECM for chafing, pinching, or contact with ground; repair any damage.
4. With key on, engine off, measure EOT signal voltage at the sensor connector and compare to expected range; a near-zero voltage suggests a short to ground.
5. Disconnect the EOT sensor and measure sensor resistance/voltage behavior; a shorted sensor will show abnormally low resistance or voltage.
6. Check ECM reference voltage and sensor ground circuits for integrity; compare readings to other temperature sensors on the same reference.
7. If wiring and sensor test normal, evaluate ECM input for internal fault after confirming all external circuits are correct.

Parts and tools you may need

• Digital multimeter
• Scan tool capable of Navistar three-digit codes
• Wiring diagram for DT466E engine harness
• Contact cleaner and dielectric grease
• Basic hand tools for sensor access

Tools you’ll need

• digital multimeter — Measures EOT signal voltage near zero and sensor resistance to confirm a short to ground versus a failed sensor.
• OBD-II scan tool — Reads DTC 311, freeze-frame data, and monitors live EOT PID to verify repeatability after repairs.
• wiring repair kit — Repairs chafed or grounded EOT signal wiring and restores proper insulation to the ECM circuit.
• electrical contact cleaner — Cleans corrosion and oil intrusion from the EOT connector to eliminate low-resistance paths to ground.

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 wiring checks, or if multiple sensor codes appear together, have the ECM inputs and harness tested by a qualified diesel technician. Do not attempt high-pressure oil system service for this code; DTC 311 is a sensor-circuit fault, not an HEUI pressure issue.

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.

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