SPN 84 — Wheel-Based Vehicle Speed
System: Vehicle / ABS
Vehicle road speed calculated from a wheel or output-shaft speed signal.
Can I keep running it?
MEDIUM — fix soon
Speedometer, cruise and speed limiting may misbehave. Safe to move carefully to a shop.
Likely causes
- Damaged or dirty vehicle speed sensor
- Wrong sensor air gap or damaged tone ring
- Wiring damage
- Incorrect tire size or axle ratio programmed
Checks & fixes (easiest first)
- Inspect the speed sensor and tone ring for debris and damage
- Measure sensor resistance and AC output while turning
- Check the parameter programming for tire revs/mile and axle ratio
- Look for ABS codes that point to the same sensor
Common FMIs with SPN 84
- SPN 84 FMI 2Data erratic, intermittent, or incorrect
- SPN 84 FMI 8Abnormal frequency, pulse width, or period
- SPN 84 FMI 10Abnormal rate of change
Related codes
- SPN 190Engine Speed
FAQ
What does SPN 84 mean?
SPN 84 is Wheel-Based Vehicle Speed. Vehicle road speed calculated from a wheel or output-shaft speed signal.
Can I keep running with SPN 84?
Speedometer, cruise and speed limiting may misbehave. Safe to move carefully to a shop.
What causes SPN 84?
Damaged or dirty vehicle speed sensor; Wrong sensor air gap or damaged tone ring; Wiring damage; Incorrect tire size or axle ratio programmed.