Hello fellow Lexus lovers, I’m in desperate need of help. I have owned 3 Lexus’ in my short 22 years of life thus far, and am in love with the 90’s-2000’s Japanese tuner scene. I own a 1998 Lexus gs300 with just over 210k miles, and am getting thrown a P0715 code, which is a turbine speed sensor circuit malfunction. I’ve replaced my input speed shaft sensor, and even established there is actually power reaching the sensor. She cranks like butter, but simply refuses to stay on for more than 10 seconds without it puttering out. I’ve checked all hoses, no rips, everything is bolted properly, so there’s no chance of air leaking from the plenum or hoses. I just replaced the fuel pump a month ago so I know and can hear the fuel pump engage prior to cranking. I know it’s not related to the motor, as I just replaced valve cover gaskets, spark plugs, coil packs, and just replaced the oil and filter along with resealing the pan. Cams look clean, and it’s a stock 2jz, so I’m not worried about it blowing up ever. Im sure it’s something related to the trans, but I’ve replaced the speed sensor and replaced the trans fluid (no shavings or discoloration of fluid). I’m running out of possible ideas, and this is currently my daily driver. Given my financial circumstances, I’m not where I can go and pay $200 to tow it to a mechanic, just for him to charge me another $300 for an hour and a half of diagnosis. I can send a video of it cranking and then puttering out, if need be. If any of you have any suggestions I would greatly appreciate it. Thank you all for your time, I hope you all have a blessed day🙏

 

By the input speed shaft sensor do you mean the O/D Direct Clutch Speed Sensor?

There are only 4 things that could cause this code: The sensor, The sensor wiring, the ECM, or the Transmission
The first thing I would do is access a code scanner which can read some data, you may be able to read the PID reading from the sensor. If you can read the O/D direct speed to be 700-800rpms (at idle), than you can move on to testing the sensor. If you cannot, the ECM is bad
Next, you said you verified power going into the sensor which im assuming means you have a meter of some sort. Remove the sensor and connect your meter between the power and ground pins. Wave a magnet around the sensor, the sensor should intermittently flash some voltage as the magnet goes around it. If you can verify that, than it is good. If you have an ohmmeter. Resistance should be 560-680ohms. If you cannot verify, replace the sensor. If you can verify, the wiring from the sensor to the ECM is bad.
Despite all of this, you could also have a bad transmission. But if it was driving one day, then stopped working the next. I would safely rule this factor out.