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SPN 1761 FMI 2

Aftertreatment 1 DEF Tank Volume — Data erratic, intermittent, or incorrect.
The signal jumps around, drops in and out, or disagrees with other information the controller has.

What the SPN covers: How full the diesel exhaust fluid (DEF) tank is. More on SPN 1761.

What FMI 2 usually points to: Loose or corroded connectors, chafed wiring, a failing sensor, or two redundant sensors that do not agree. More on FMI 2.

Severity

MEDIUM — fix soon

Running low on DEF leads to inducement derates and eventually a speed limit. Fill up.

Likely causes

  1. Low DEF level
  2. Frozen DEF
  3. Faulty level sensor (often combined with temperature/quality sensor)
  4. Wiring fault

Checks & fixes (easiest first)

  1. Fill the tank with fresh, certified DEF
  2. Check the tank sender for crystal buildup
  3. Compare gauge with a visual check

FAQ

What does SPN 1761 FMI 2 mean?

Aftertreatment 1 DEF Tank Volume — data erratic, intermittent, or incorrect. The signal jumps around, drops in and out, or disagrees with other information the controller has.

Is SPN 1761 FMI 2 serious?

Running low on DEF leads to inducement derates and eventually a speed limit. Fill up.

What should I check first for SPN 1761 FMI 2?

Fill the tank with fresh, certified DEF; Check the tank sender for crystal buildup; Compare gauge with a visual check.