Transmission oil temperature too high
The sensor is working and the reading is real, but the value is dangerously high. This is the engine telling you it has a mechanical or system problem, not a wiring problem.
SPN 177 — Transmission oil temperature too high
SPN 177 is the parameter the ECM is flagging on All makes engines. The FMI that comes with it tells you how it failed. Each failure mode below has its own causes and its own test order — do not treat them as the same repair.
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Every SPN and FMI page on this site stays open — no account needed. Pro members can take the code into Blue Collar AI with the VIN, symptoms and photos, keep per-truck history, and print a work order. $14.99 a month or $99.99 a year.