The MLPS or manual lever position sensor is one of the vitally important inputs to the transmission control unit (TCU) of a vehicle with modern computerized automatic transmission. Every car made in the last 50 years has a switch similar to an MLPS. The names range from MLPS, to inhibitor switch to neutral safety switch.
Originally called a neutral safety switch when introduced to the automotive field because it’s only duties were to make sure the car only start in neutral and park, and to activate the reverse lights when you shift into reverse.
As automatic transmissions became more technically advanced the MLPS duties increased. Now the MLPS or inhibitor switch is a key input to the TCM and ECM on every modern car I can think of. In fact, the switch, whatever name you call it has a great deal to do with controlling what gear your automatic transmission is in and how it shifts, and when the torque converter locks up, as well as it’s original duties.
In most cases the switch is located on the side of the transmission, essentially hooked to the shift lever in the car. That way when you move the lever, it moves the switch to the appropriate gear range. some cars have a remote mounted switch, however the responsibility remains the same.
On transmissions with a side mounted switch, GotTransmissions.com often provides a new switch with their transmissions where failure’s are more prevalent. If it is not included with the transmission, it is a good idea to scan the car before any transmission work is done to make sure that did not cause the problem. At my shop, we almost always changed every one when we did a rebuild on a transmission. Either way, I would advise putting a new factory MLPS on your car if you do have to exchange a worn out transmission for a rebuilt transmission, unless it is cost prohibitive.
Most of the time when an MLPS goes bad, you will know you have something wrong with it. This is the time to have it checked by a qualified transmission mechanic at a competent transmission shop.
Many folks who own affordable hand held code readers can find out what the problem is before hand. In many cases if you are mechanically handy you can change it yourself. If you choose to take that route. don’t forget to clear the code and re-drive the vehicle and recheck to make sure you cured the problem.
These particular switches are on the outside of the car as we mentioned earlier and are exposed to the road elements. Therefore causing a hi rate of failure. Geographically speaking, problems can occur from salt being used to melt snow in the north to water damage from a heavy rain.
Don’t forget to properly maintain your transmission on a regular basis. Feel free to sign up for our GotTransmissions.com blog for free. You may find more money saving and drive-ability tips in your mailbox regularly.
