SPN 1761: Aftertreatment DEF Tank Level
What SPN 1761 Is
SPN 1761 is Aftertreatment 1 Diesel Exhaust Fluid Tank Level — the sending unit in the DEF tank header. It reports percent remaining to the ACM/ECM. Empty DEF, a failed sender, or a rotten header connector all set this SPN. It is not outlet NOx (SPN 3226).
Cummins often surfaces this as FC 1682 / related tank-level faults. Low level with no other aftertreatment codes is frequently a real empty tank or a gauge that does not match the dash.
Common FMI Combinations
| FMI | Meaning | Start here |
|---|---|---|
| 1 / 17 / 18 | Level below normal | Look in the tank. Then sender. |
| 3 / 4 | Voltage high / low | Header connector, harness to ACM |
| 5 | Open circuit | Unplugged header, broken wire |
| 9 / 10 | Update rate / rate of change | Datalink to the tank module |
| 13 | Out of calibration | After header replacement |
Diagnostic Order
- Open the tank. Confirm fluid. Contaminated or diesel-in-DEF is a quality (3364) job, not a level job.
- Inspect the header connector. DEF crystals here are the number-one no-parts fix.
- Compare dash percent to live data. If live data is 0% and the tank is full, sender or wiring.
- If level is truly low, inducement SPN 5246 will follow. Fill with API-certified DEF, then re-evaluate. Do not clear inducement and send the truck.
A $2 connector cleaning can save a $400 header assembly. Clean, dry, dielectric, latch it, then retest.
On a remote session we use a Nexiq USB-Link 3 and a diagnostic laptop to graph DEF level, tank temperature, and companion quality codes while you are at the tank.
Frequently Asked Questions
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A Torque Edge technician can connect live with a Nexiq USB-Link 3 and a rugged diesel diagnostic laptop. If you already have an adapter, we use yours. If you don't, we have the kit on our side — you don't wait on a dealer.
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