P0503 Code: Vehicle Speed Sensor “A” Intermittent/Erratic/High

The vehicle speed sensor (VSS) keeps track of how fast the vehicle is going. It sends its readings to the speedometer and the powertrain control module (PCM). The PCM uses the speed reading to adjust various processes. VSS data also goes to the control modules that run important systems such as the transmission, ABS traction control, and power steering.

 If the VSS is underperforming or making noise, the PCM will log a P0503 code.

What Does P0503 Mean?

The diagnostic trouble code (DTC) P0503 indicates “Vehicle Speed Sensor “A” Intermittent/Erratic/High.”

Other names for this DTC code include:

• Vehicle Speed Sensor (VSS) Malfunction
• Vehicle Speed Sensor “A” Range/Performance
• Vehicle Speed Sensor “A” Low Input

Depending on the design of the vehicle and its VSS, the vehicle speed sensor may be found on the differential, speedometer head, transmission, or transaxle.

Most VSS calculate the vehicle’s speed based on the speed of the transmission output shaft. Some sensors measure the differential gear’s speed or use the readings provided by the wheel speed sensors. No matter where the vehicle speed signal comes from, the VSS gives real-time data on how fast the vehicle is going.

The PCM regularly checks the vehicle speed sensor. If the computer doesn’t get the right response from the sensor, it will set the generic powertrain code P0503.

Note: The definition of code P0503 can differ according to the vehicle manufacturer. Check the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0503 Code?

• Problem with the PCM or other module
• Short or open wire leading to VSS or issues with connectors
• PCM not configured for the tire size being used (this won’t usually set a P0500)
• Damaged drive gear

What are the Common Symptoms of the P0503 Code?

• Illuminated check engine light
• Malfunctioning speedometer
• Erratic shifting with an automatic transmission
• Inactive or erratic ABS performance
• Traction control not engaging or engaging when it shouldn’t

How to Diagnose the P0503 Code

The P0503 code is a generic powertrain code that various makes and models can log. However, this does not mean that there is a one-size-fits-all solution to identify its underlying problem.

If you’re not confident about conducting diagnostic tests on your vehicle, it’s a good idea to bring it to a professional mechanic. Otherwise, you can go ahead and diagnose the issue yourself. To help you get started, here is a video that can give you an idea of what the process might involve:

How to Fix the P0503 Code

Attempting to fix a P0503 code can become a challenging task if you don’t have the right tools and know-how to test the vehicle speed sensor. In most cases, it’s best to leave the job to professionals.

For DIYers with advanced technical knowledge and hands-on experience who prefer to test and replace their vehicle’s vehicle speed sensors on their own, it will be helpful to rely on the appropriate repair manual or refer to an online repair database.

Where to Get Replacement Parts to Fix Code P0503

A damaged drive gear is one of the common issues that can cause the PCM to log this trouble code. Fortunately, it’s not too difficult to find a replacement that’s compatible with your vehicle at CarParts.com.

Simply enter your ride’s year, make, and model into our vehicle selector after searching for the part you need to narrow down the results to compatible products. Then, choose from our wide selection of replacement parts that come at competitive prices.

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