Recently speaking with another turbo-mopar member I complained that after I thrash on the Charger and come to a stop the idle is running at 2000 rpm. He told me that the speed sensor is the usual cause of this problem.
I could only find scant info on this mysterious part and decided to know more. I had an allegedly bad one in my parts, so I disassembled it. No easy task. Here are the results. As you probably know there is a gear on one end that is driven by a shaft in the transmission. At the top is a connection for the speedo drive cable. The port that you plug the wires into has two pins which are connected to a magnetic reed switch. My multimeter showed me that the switch is normally open. On the main shaft of the sensor is a disk with 8 small magnets embedded in it. A signal from 2-14 of the LM provides a potential on one side of the switch. The disk is in close proximity to the switch and when the magnet passes by the switch the magnetic field closes the switch momentarily sending the signal to a ground. The computer counts each of these pulses and the computer processes them. Beyond that I do not know how much effect this has on the operation of the car. Hopefully someone on the site can elaborate further. At this point my only choice is to buy a new sensor unless some can give me a another cause for the high rpm idle. Usually I can turn off the engine and restart and the idle is back to normal Attachment 62058













Attachment 62058