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P0502– What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

Vehicle Speed Sensor Low Input

Meaning

The P0502 code is one of the OBD-II generic codes. It means that there is a problem with your vehicle's speedometer or speed sensor.

A code reader will also give you the address of the DTC trouble code by displaying it on its display screen

If you're driving, wait until you find a safe place to pull over before stopping to turn off your engine and verify your odometer reading, then write down your current mileage. After verifying this information, make sure that no warning lights are coming on; if they are, check for problems as soon as possible.     

Even if there aren't any warning lights coming on when you first notice an issue, troubleshooting certain issues can be difficult without experiencing them after the vehicle has been warmed up. So, try to remember how your car was running before you noticed any problems with its speedometer or sensor.

Causes

 A P0502 code could mean that one or more of the following has happened:

  • There is an issue with your vehicle's speedometer 
  • There is an issue with your speed sensor 
  • The problem is linked to wiring and/or switch issue 
  • Your Engine Control Module (ECM) needs to be reset  A loose connection to the ECM can cause this p0502 trouble code. Check all connections related to the speedometer, such as the VSS (Vehicle Speed Sensor). A loose or poor connection will cause problems like this one, and will need to be repaired before any testing should be done on any other components in this system. A bad wheel bearing can also cause the speedometer to not work properly, especially if it is making noise.

Symptoms

Symptoms of a P0502 code may include:

  • Erratic speedometer and/or odometer readings 
  • Vehicle pulling to one side when driving at steady speeds 
  • Strange sounds coming from the engine bay whenever you're driving, especially if accompanied by other symptoms like this one 
  • Other warning lights coming on that could be indicative of a more serious problem such as an overheating engine or even a fire. 

Diagnosis

It is relatively easy to determine the cause of this code. You'll need a scan tool that can interact with your car's ECU in order to find out exactly why the speedometer isn't working properly. If all connections are intact and there aren't any broken wires, then it would be safe to say that there is an issue with either the VSS or the sensor itself. To check for sure what's causing your P0502 code use an ODB-II scanner.

Common mistakes

Because the speedometer on the vehicle is inaccurate, replacing the instrument cluster is a common mistake that can be made when this trouble code is stored. The vehicle speed sensor transmits data to the instrument cluster, so check there first.

What repairs can fix the code?

P0502 can be repaired by performing the following:  

  • Making sure the wheels and tires on the vehicle are the right size
  • A wheel speed sensor or sensors needs to be replaced
  • The replacement of a hub bearing
  • Removing and replacing the instrument cluster
  • Fixing or replacing the wiring and connectors in the circuit that detects vehicle speed
  • Installing a new speed sensor on a vehicle

Conclusion

P0502 is a diagnostic trouble code (DTC) for "Vehicle Speed Sensor Low Input". It's important to know that this condition does not always indicate an engine problem, but can be caused by other factors such as speed sensor wiring issues. To diagnose the issue and fix it if necessary, you'll need to use your OBDII scanner or scan tool to check the vehicle’s computer system. You may also want to refer to your car manual so you have all of the information needed before contacting a mechanic.