P0502: Vehicle Speed Sensor A Circuit Low
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes with care - expect cruise control and some driver aids to be unavailable.
Symptoms
- Speedometer reading zero
- Cruise control disabled
- Transmission stuck in gear or shifting late
Likely causes, most common first
- Speed sensor circuit open or shorted low
- Broken wire in the sensor circuit
- Failed sensor
- Connector corrosion
Read P0502 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0502 is a low or missing vehicle speed signal. Without it the transmission cannot schedule shifts properly, which is why a dead speedometer and a transmission that suddenly shifts at the wrong moments so often arrive together.
On older vehicles the sensor is a discrete part in the transmission or transfer case and is straightforward to replace. On newer ones the speed signal is derived from the anti-lock brake wheel sensors and sent over the data bus, so this code may point at a wheel sensor or a communication fault rather than at any part called a speed sensor.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Cars that report P0502 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0502?
Yes with care - expect cruise control and some driver aids to be unavailable.
How much does it cost to fix P0502?
Typical US repair costs range from $60 for the simplest fix (vehicle speed sensor) to $450 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0502. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.