P0502

Vehicle Speed Sensor A Circuit Low

Vehicle speed / powertrain control Generic OBD-II High

What it means

P0502 means the vehicle speed sensor (VSS) signal is abnormally low or missing. Many systems depend on this signal — speedometer, odometer, cruise control, transmission shift timing, and often ABS/traction control — so a lost signal causes a cluster of symptoms. The usual causes are a failed sensor or a wiring short/open in its circuit.

High

Can I keep driving? Drivable but degraded — the speedometer, cruise control, and transmission shifting rely on this signal, so expect erratic shifts and lost cruise. Have it fixed promptly.

Real-world scan data

Seen in

533

scans in the past year

Found in

0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of P0502 scans

P0704in 21.6% of scans

P0401in 18.8% of scans

P0504in 18.8% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Inaccurate or dead speedometer/odometer
Harsh, erratic, or delayed transmission shifts
Cruise control disabled
ABS or traction-control warning light (shared speed data)

Common causes

Most likely first

Failed vehicle speed sensor (low or no signal)Likely
Short to ground or open in the sensor signal wiringCommon
Loose or corroded connector at the sensorCommon
Damaged sensor reluctor/tone ringLess often
ECM/PCM fault (rare)Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data and confirm the code with a scan tool.
Inspect the speed sensor connector and wiring for a short to ground or open.
Check the sensor and its tone ring for damage or debris.
Back-probe the signal while turning the wheel/driveline and watch for a reading.
Replace the speed sensor if it produces no valid signal. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0502?+

It runs, but the speedometer, cruise, and shifting can misbehave, and ABS/traction may drop out. Drive carefully and fix it soon.

Can I just clear P0502?+

It returns until the sensor or wiring is repaired. The transmission and speedometer need a valid speed signal.

Read & clear P0502 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX