Cummins 1691 (ISB, ISC, ISL)
What this code means
Cummins fault code 1691 (SPN 100 / FMI 18) refers to: (ISB, ISC, ISL). It is logged by the engine control module (ECM) on Cummins-powered vehicles and read over the J1939 diagnostic network.
Emissions system
This is an emissions after-treatment related fault on the DPF system. On Cummins-powered vehicles it is commonly seen when that after-treatment system is faulty, restricted, or has been modified.
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Frequently asked questions
Cummins fault code 1691 (SPN 100 / FMI 18) indicates (isb, isc, isl).
Cummins 1691 is generally treated as a moderate-severity fault. Have the engine and its wiring inspected, and confirm the reading with a J1939 diagnostic scan before clearing the code.
Yes. Cummins 1691 is associated with the DPF after-treatment system on Cummins engines.
