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SPN 520 FMI 9

Actual Retarder – Percent Torque — Abnormal update rate.
Expected data is arriving too slowly or has stopped arriving over the data link.

What the SPN covers: How much braking torque the retarder or engine brake is actually producing, as a percentage. More on SPN 520.

What FMI 9 usually points to: A module that has dropped offline, a network wiring issue, or a module that is overloaded or resetting. More on FMI 9.

Severity

MEDIUM — fix soon

Your engine brake or retarder may not work. Drive with extra caution on grades.

Likely causes

  1. Retarder or engine brake control problem
  2. Network message missing or invalid
  3. Faulty retarder module or sensor

Checks & fixes (easiest first)

  1. Check for other network codes and the module that sends this data
  2. Inspect the J1939 backbone and terminating resistors
  3. Check retarder/engine brake operation and switch inputs
  4. Check for J1939 network codes
  5. Check codes in the retarder or transmission module

FAQ

What does SPN 520 FMI 9 mean?

Actual Retarder – Percent Torque — abnormal update rate. Expected data is arriving too slowly or has stopped arriving over the data link.

Is SPN 520 FMI 9 serious?

Your engine brake or retarder may not work. Drive with extra caution on grades.

What should I check first for SPN 520 FMI 9?

Check for other network codes and the module that sends this data; Inspect the J1939 backbone and terminating resistors; Check retarder/engine brake operation and switch inputs.