SPN 171 — Ambient Air Temperature
System: Sensors
Outside air temperature, used for cold-start strategies and engine protection.
Can I keep running it?
LOW — usually OK to keep running
Minor; may affect cold-start and fan behavior.
Likely causes
- Faulty sensor (often in the mirror or bumper)
- Wiring fault
- Network data missing from the module that owns the sensor
Checks & fixes (easiest first)
- Compare reading to actual outside temperature
- Inspect sensor and connector
- Check whether the value comes from another module over J1939
Common FMIs with SPN 171
- SPN 171 FMI 2Data erratic, intermittent, or incorrect
- SPN 171 FMI 3Voltage above normal or shorted high
- SPN 171 FMI 4Voltage below normal or shorted low
- SPN 171 FMI 19Received network data in error
FAQ
What does SPN 171 mean?
SPN 171 is Ambient Air Temperature. Outside air temperature, used for cold-start strategies and engine protection.
Can I keep running with SPN 171?
Minor; may affect cold-start and fan behavior.
What causes SPN 171?
Faulty sensor (often in the mirror or bumper); Wiring fault; Network data missing from the module that owns the sensor.