P0503 code meaning
Vehicle Speed Sensor A Circuit Intermittent/Erratic/High
Powertrain system Generic code P05xx codes Check engine light
What P0503 means
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 deceleration and raises the fan.
P0503 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0503
- Check engine light on
- Speedometer needle jumps
- Cruise control drops out, jerky shifting
Common causes of P0503
- Most likelyLoose contact, chafed wire, corroded connector
- PossibleInterference from damaged shielding or the ignition
- PossibleSensor with weakened magnet or damaged tone wheel
- Less likelyABS/ESP fault (signal source)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Vehicle speed sensorABS moduleSensor wiringEngine control module
What each part of P0503 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 03 | The exact fault in that area. |
What to do next
- Note P0503 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0503
What does P0503 mean?
P0503 means "Vehicle Speed Sensor A Circuit Intermittent/Erratic/High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0503?
Drive gently and only to a workshop. With P0503 the car can go into limp mode (reduced power) to protect itself.
Will P0503 fail an emissions test?
Yes, it can. P0503 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0503 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0503 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.