How is the VSS sensor used in the PCM?
How is the VSS sensor used in the PCM?
OPERATION The Vehicle Speed (VSS) Sensor input is used by the PCM to determine vehicle speed. The VSS generates a signal that increases in frequency proportionate to vehicle speed. The PCM has a base frequency stored in memory for a distance of one mile.
How does a speed sensor work on a PCM?
Being that the PCM reads this sensor in a voltage drop fashion, an open circuit in any of the three wires or internally to the DPFE will result in 5 volts being displayed on the scan tool as well as found at the sensor with a DVOM. Crank sensors, cam sensors, wheel speed sensors and other “speed” sensors work on similar principles.
What should the voltage be on my ECM PCM sensor?
If the meter reads 5.0 volts, the electrical circuit is good. If the meter reads other than 5 volts, ground one meter lead and test the 5 volt reference wire. It should read 5 volts. If it doesn’t you have a wiring or computer problem. Using the wiring diagram check the pin at the computer that supplies the 5 volts.
What can change the speed of a VSS sensor?
Modified drivetrain components such as final gear sets and/or tires can alter VSS input values to the PCM. Improper signals can alter Torque Converter Clutch (TCC) application, shift points, cruise control operation as well as many other systems relying on vehicle speed input.
If the meter reads 5.0 volts, the electrical circuit is good. If the meter reads other than 5 volts, ground one meter lead and test the 5 volt reference wire. It should read 5 volts. If it doesn’t you have a wiring or computer problem. Using the wiring diagram check the pin at the computer that supplies the 5 volts.
How can I tell if my PCM is faulty?
You need to check the sensors that are connected to your PCM, as well as the wires that connect them. If you’re seeing a PCM code – or two, or three – it can really help you narrow in on which sensors or wires are faulty.
Can a meter be used to test VSS sensors?
While a meter can be used to test VSS sensors, it’s much better to test them with an oscilloscope. A scope allows you to view the sensor signal waveform pattern and check for any inconsistencies. A magnetic pickup sensor will produce an alternating sine wave pattern.
How does the PCM work in a car?
Many of your car’s functions are controlled by the powertrain control module (PCM), which works in conjunction with the engine control module (ECM) and transmission control module (TCM) to adjust engine timing, the air to fuel ratio, and other systems. So before we talk about how to test a PCM, here are some common symptoms of a PCM failure.
