P0500 Code: Vehicle Speed Sensor (VSS) Malfunction

Has your system set a P0500 code? Let’s explore what the code means and what might cause it.

What Does the P0500 Code Mean?

Diagnostic trouble code (DTC) P0500 stands for “Vehicle Speed Sensor (VSS) Malfunction.” This code is set when the PCM or engine control module (ECM) detects incorrect speed readings or no signal at all from the vehicle speed sensor (VSS). Some vehicle platforms don’t list this code but will set similar P050x codes, e.g., P0501, etc.

Other names for this code include:

• Vehicle Speed Sensor “A” Range/Performance
• Vehicle Speed Sensor “A” Intermittent/Erratic/High
• Vehicle Speed Sensor “A” Low Input

If you wish to understand the technical details of how the vehicle speed signal is used by different systems in a car, you can read our discussion here.

To learn the possible causes of code P0500, read the next section.

What are the Possible Causes of the P0500 Code?

As mentioned, speed sensors vary in type. This could mean that the causes may also differ as to the VSS mechanism. Here are the common causes that trigger code P0500:

• Defective vehicle speed sensor
• 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 P0500 Code?

Below are the common symptoms you may face if your OBD-II scan tool is showing the P0500 code:

• 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 P0500 Code

It might be difficult to figure out what exactly triggered the P0500 code, which is why people often leave the diagnosis to a mechanic. If you feel confident enough in your DIY auto repair skills, however, you can probably pinpoint the cause by following the videos below:

How to Fix the P0500 Code

Since there are several possible causes that could trigger the P0500 code, there’s no single way to fix it. Because of this, you’re probably better off having a professional mechanic fix your car for you.

Of course, you can decide to resolve the P0500 code on your own if you have the necessary DIY skills. As discussed above, you’ll first need to diagnose the problem before you can fix it. You can check repair manuals and online auto repair resources and guides to help make sure you’re on the right track.

You can also invest in an ALLDATA single-vehicle subscription, which should be useful not just for this repair but for other future fixes you may need to do on your car.

Always remember that different carmakers have their own specific repair instructions for their vehicles, so what works for one model may not work for a different one. Make sure to consult your repair manual before working on your car.

How the Vehicle Speed Signal is Used By Different Systems

The earliest vehicle speed sensors were used for cruise control (a.k.a. “Speed Control”), which is one of the earliest examples of a closed loop system to be used on an automobile. Any closed loop system uses an input to determine output control. The thermostat in a building’s climate control system is a good example of a closed loop system designed to measure ambient temperature in a building and engage or disengage the air conditioning or heating system to maintain the air temperature inside that building.

Cruise control works in a closed loop fashion as well. In order to control vehicle speed, the Cruise system needs to know how fast the vehicle is going and the vehicle speed sensor provides that information. There are two-wire and three-wire vehicle speed sensors, and the vehicle speed signal can be analog (sine wave) or digital (square wave). Usually, the vehicle speed sensor is measuring the speed of the transmission output shaft, but it can also measure the speed of the differential gear or even the wheel speed sensors.

Older vehicles used a cable connected to the transmission output shaft by way of a plastic gear to drive the speedometer, and some vehicle speed sensors were even built into the speedometer itself on certain Asian vehicle makes. But speedometer cables began to disappear in the ‘80s until eventually all speedometers depended on an electronic sensor.

Initially, electronic speed sensors delivered their signal directly to the speedometer and the cruise control module, then as engine control modules (ECMs) became a thing, the speed signal was also delivered to that module as well.

Then with the advent of anti-lock brakes (ABS), on some ABS systems, the ABS module uses wheel speed sensor input to generate vehicle speed information that is delivered to the ECM/PCM and/or the instrument cluster module. Some vehicles have the vehicle speed sensor delivering VSS input to some module such as the smart fuse panel or junction box, where it is processed and sent out to the various modules that use the vehicle speed signal.

The speedometer and cruise control both obviously need vehicle speed information, but the ECM/PCM/TCM module uses the vehicle speed signal for other things, like transmission shifts on an electronic transmission, vehicle speed limiting,  The body control module (BCM) usually monitors vehicle speed for a variety of reasons, one of which would be variable assist power steering or to extinguish the interior lights above a certain speed if a door ajar switch has failed and is keeping the lights on when they shouldn’t be.

Regardless of the path the vehicle speed signal takes from its generation to the module(s) receiving the signal, the VSS is required to provide real-time information concerning vehicle speed. And if the modules believe the vehicle is sitting still when it’s actually moving, there will be symptoms ranging from an inoperative speedometer and odometer to an automatic transmission that won’t shift automatically. The VSS signal can be inaccurate or erratic, which causes different but similar symptoms.

Again, there are many different types of vehicle speed sensors and systems, and knowing where the vehicle speed signal originates is necessary before you even attempt to troubleshoot a P0500.

Some linear automatic transmissions will have a sensor reading the speeds of the turbine shaft, the intermediate shaft, and the output shaft in the transmission for shift scheduling and transmission fault detection.

Get Parts To Help You Fix the P0500 Code

The P0500 code isn’t a code you should ignore, since it deals with your transmission’s ability to shift gears and your vehicle’s traction control. If a faulty VSS or a problem with the PCM is causing these issues, it would be best to replace them. Good thing CarParts.com is a one-stop shop for all sorts of vehicle parts.

CarParts.com has a wide selection of engine parts for a lot of different vehicles. Our parts are built to match your original part’s specifications, fit, and function, ensuring a perfect fit. They’ve also been tested during manufacturing, ensuring reliability and durability. Order now, and your new sensor can arrive in as fast as two business days, thanks to our strategically located warehouses.

Don’t wait for the problem to snowball before taking action. Shop for a new PCM or speed sensors here at CarParts.com today!

Products Mentioned in this Guide

Speed Sensor Speedometer