I scanned my car with a code reader. My transmission has been acting up but it doesn't seem mechanical. When the engine first starts, the tranny shifts fine but after a few minutes it just completely stops working. Its like the automatic clutch is engaging. I suspected a transmission speed sensor.

The codes are

P0500
Vehicle speed sensor A

P1759
Front brake Valve solenoid.

From what I read, the speed sensor sends a signal to the TCM and then from there the signal is sent to the front brake valve solenoid. So it would make sense to have those two codes together. I'm not 100% sure on all of this but its a good guess. Some guy tried to tell me it would cost $3100 and I felt like that was BS. Another mechanic also said it was some type of sensor or solenoid that was bad. He doenst repair trannys, only replaces so he wouldnt go any further. I just don't know how to order the correct part. Vehicle speed sensor A?

 

2003 G35 coupe 155k btw

 

Both the ECU and TCM monitor vehicle speed. The Ecu has 4 vehicle speed sensors that it uses to monitor each wheel. The TCM has an internal revolution VSS that it uses. Both computers have a different trouble code they will send if sees a problem with a VSS, the TCM will actually use the wheel sensors as a back up if it's own internal sensor fails. The p0500 code is being sent from your ECU, it has decided that one or a few of its wheel sensors are not reading correctly. The p1759 is coming from your TCM, it is trying to tell you that there is something mechanically wrong with the hydraulic system that controls your front brakes. The TCM's internal diagnostic system has determined that your wheels may not be spinning freely and has gone into failsafe mode by shutting down ATF pressure switch 1. It keeps the trans safe by keeping it from shifting. The ecu's speed sensor would not read correctly either in this scenario and you should also experience shift shock when moving from a standstill.

The circuit you described is actually part of the Vdc/slip/abs system and uses the transmissions internal speed sensor (not the one you have a code for)... along with the ecu speed sensors, steering angle sensor, throttle position sensor, accelerator position sensor, and g force sensors to keep you from getting too damn crazy. It never does any good to guess at what these cars are up to electronicly because Japanese people really like puzzles.