P0503: Vehicle Speed Sensor Circuit Intermittant

What Does Code P0503 Mean?

The (VSS) Vehicle Speed Sensor provides an actual vehicle speed signal to the Powertrain control module (PCM or ECM). The VSS is a permanent magnet generator type sensor also known as a hall effect sensor. The sensor produces an AC voltage as the toothed gear on the transmission output shaft passes through the sensor magnetic field. The voltage produced and the number of pulses will increase as the vehicle travel speed increases and pulses will decrease as speed decreases. The computer converts this voltage signal into a vehicle speed number. The PCM uses the VSS signal to control transmission shift timing and the torque converter (TCC) clutch apply.

How The Code Is Set

If the computer detects a drastically large or small sensor signal out of the normal range depending on vehicle speed or a loos then re-gain of the signal, then DTC P0503 sets.

Code P0503 Symptoms

• Check Engine Light on
• Speedometer not working or intermittant
• Transmission shift problems
• ABS light on dash
• traction warning light

Common Causes of Code P0503

• A fualty vehicle speed sensor
• VSS sensor intermittant open circuit
• Sensor circuit poor electrical connection
• A faulty powertrain control module

How to Diagnose P0503

First, disconnect the sensor harness connector, visually inspect the wiring harnesses and connectors. Slightly tug on each of the two wires slightly to see if one of them breaks or stretchess. Look for broken, bent, pulled out or corroded terminals inside the VSS connector. If you have a computer scanner that shows live sensor data plug the connector back in, you can jack up the drive wheels, put the car in drive or spin the wheels manually and watch the data of the sensor. Or you can have someone watch the speedometer. While wiggling the connector, see if the live data or speedometer needle fluctuates, goes out or comes on goes. If this does happen, then the problem is in the wiring at or near the sensor. If there is no change, do the same thing of wiggling the wiring all the way from the sensor to the computer. If stil no change, then the most likley cause is the sensor itself. This is a fairly inexpensive sensor and easily replaced.

See Electrical Testing

What Will Fix Code P0503?

After proper diagnosis, replacing the sensor, fixing wiring or replacement of the computer. The sensor is very easy to replace and only requires that you remove one bolt and then pull the sensor out. Be sure to put a little grease or oil on the new sensors O' ring to help in installation. Clear all the computer codes after any repairs are made and take for a test drive.