International A26 SPN 1761 FMI 1 — DEF Tank Level Below Normal

Code Details

Plain-English Meaning

The International A26 engine uses a DEF system to keep NOx emissions within required limits. When the DEF tank level drops below the calibrated low-level threshold, the engine control system starts an inducement sequence. The driver sees a warning lamp and may get a dashboard alert. If the DEF is not replenished within a set number of miles, the engine will reduce torque and eventually cap road speed. Adding DEF and resetting the fault with ServiceMaxx returns the truck to full operation.

SPN 1761 is Aftertreatment 1 DEF Tank Level in J1939. FMI 1 means the measured level is below the normal operating range. On International A26 engines in LT and RH Series trucks, the DEF system is managed by the engine ECM and a dedicated aftertreatment control module. The DEF tank sensor feeds a continuous level signal; when it falls below the calibration threshold, SPN 1761 FMI 1 is logged and the distance-based inducement sequence begins. International ServiceMaxx provides access to the live DEF level sensor data, current inducement stage, accumulated distance, and the inducement reset procedure.

Common Symptoms

• Amber DEF or aftertreatment warning lamp on the International instrument cluster
• DEF level low or SCR fault message on the International driver display
• Progressive torque reduction as the inducement advances past the initial warning
• Inducement stage and distance-to-restriction data visible in ServiceMaxx or fleet telematics
• Speed restriction in the final inducement stage until DEF is restored and the fault is cleared

Possible Causes

Possible causes may include the items below. The list is not a parts diagnosis.

• DEF tank genuinely depleted below the low-level threshold
• DEF level sensor or integrated module failed, reporting a false low reading
• Wiring or connector fault between the DEF level sensor and the control module
• DEF filler cap seal degraded, allowing gradual loss of fluid
• Tank emptied during maintenance and not refilled before the vehicle was returned to service

First Checks

• Check the physical DEF level using the instrument cluster gauge or a direct tank inspection before pursuing electrical diagnostics
• If the tank is low, add fresh DEF and monitor whether the warning resolves after a drive cycle
• Connect International ServiceMaxx and read the DEF level sensor output to compare against the actual tank level
• Check for companion aftertreatment codes such as SPN 3361 (DEF supply pressure) or SPN 3480 (dosing injector) to rule out additional system faults
• Inspect the DEF module harness and connector for corrosion or moisture damage if the tank is full but the fault remains active
• Perform the inducement reset in ServiceMaxx once the DEF level is confirmed adequate and any additional faults are resolved

Can I Keep Driving?

The A26 will initially operate with SPN 1761 FMI 1 active, but the inducement sequence escalates over mileage with progressive torque and speed restrictions. Restoring the DEF level promptly and resetting the inducement in ServiceMaxx is the standard repair.

Related Lookup Pages

• SPN 1761 topic page
• FMI 1 explanation
• Aftertreatment fault codes
• Search this code