System: Powertrain (P-Code)
SAE Standard (Generic)
Family: Vehicle Speed Sensor Circuit
Code P0502: Vehicle Speed Sensor A Circuit Low
Diagnostic & Technical Explanation
Code P0502 (Vehicle Speed Sensor A Circuit Low) sets when the ECM loses, or receives an implausible, vehicle speed signal from the primary VSS/output-shaft speed source used for speedometer, cruise control, ABS coordination, and shift scheduling. The signal is usually a toothed-wheel/magnetic or Hall-effect pickup, so the common causes are a damaged tone ring, an air-gap or debris problem at the sensor tip, a corroded connector, or chafed sensor wiring shorted to power/ground.
First-listed procedure
Rank #1
Clean tone ring and inspect sensor air gap
Easy DIY
This is the first procedure in the authored
consideration order, not a measured cause likelihood. Execute it only when its prerequisites
and diagnostic findings support it. Its cost and labor estimates (where known), the step-by-step procedure and the
remaining 3 procedure(s) are in the licensed dataset. Ordering context.
Full family: Vehicle Speed Sensor Circuit
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)