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SPN 171 FMI 19

Ambient Air Temperature — Received network data in error.
Data received from another module over the network was flagged as an error or not available.

What the SPN covers: Outside air temperature, used for cold-start strategies and engine protection. More on SPN 171.

What FMI 19 usually points to: The problem is usually in the module that sends the data, not the one that logged the code. More on FMI 19.

Severity

LOW — usually OK to keep running

Minor; may affect cold-start and fan behavior.

Likely causes

  1. Faulty sensor (often in the mirror or bumper)
  2. Wiring fault
  3. Network data missing from the module that owns the 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. Compare reading to actual outside temperature
  4. Inspect sensor and connector
  5. Check whether the value comes from another module over J1939

FAQ

What does SPN 171 FMI 19 mean?

Ambient Air Temperature — received network data in error. Data received from another module over the network was flagged as an error or not available.

Is SPN 171 FMI 19 serious?

Minor; may affect cold-start and fan behavior.

What should I check first for SPN 171 FMI 19?

Check for other network codes and the module that sends this data; Inspect the J1939 backbone and terminating resistors; Compare reading to actual outside temperature.