Powertrain, generic · Vehicle speed, idle control and auxiliary inputs
P0503 Vehicle Speed Sensor A Circuit Intermittent/Erratic/High
Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible
The vehicle speed signal A comes, depending on the maker, from a sensor on the gearbox, the transmission output speed, the wheel speeds via ABS/ESP or a CAN message; CARB explicitly names it as an input to be monitored. P0503 combines three fault patterns: sporadic signal loss, jumping values and a value that is too high. GM detects a sudden signal drop quickly (0.3 s, 5 counts, MIL on the first trip); Subaru sets it at 240 km/h or more for a cumulative 4 s, Saab's diesel above 220 km/h. In limp mode Subaru sets the speed to zero, disables fuel cut-off on overrun and raises the fan.
Likely causes
Loose contact, chafed wire, corroded connector
Interference from damaged shielding or the ignition
Sensor with weakened magnet or damaged tone wheel
ABS/ESP fault (signal source)
Symptoms
- Check engine light on
- Speedometer needle jumps
- Cruise control drops out, jerky shifting
Repair estimate
DifficultyMediumDIY possible
Parts and labour€50–350
Time0.5–2.5 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
vehicle speed sensorabs modulesensor wiringengine control module
Related codes
References: gsi.ext.gm.com, saabwisonline.com, saabwisonline.com.