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Toyota Service
Toyota Service, Lexus and Toyota expert
Category: Lexus
Satisfied Customers: 4821
Experience:  30 + years of experience; Multiple Award Winning Svc Mgr; Just Answer Customer's Choice Award Winner
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I have a 99 lexus GS300 with a code P0500. I changed the

Customer Question

Hi, I'm Brian. I have a 99 lexus GS300 with a code P0500. I changed the speed sensor at the rear of the trans, and it did not fix the problem. I then checked the live dada and all 4 wheel speed sensors read fine,but the viehicle speed is erratic on the scanner. I then made my own harness from the speed sensor to the ecu and still no change. After about a mile or so the viehicle speed will momentarily drop to 0 and the trans starts down shifting while at 40 mph. I have even replaced the ecu and still no change. I was thinking maybe the problem is in the combination meter but the speedo seems to work fine. Any Ideas?
Submitted: 1 year ago.
Category: Lexus
Expert:  Toyota Service replied 1 year ago.
Hello. Welcome to Just Answer. Please allow me to assist you. A P0500 code indicates a speed sensor issue. The speed sensor is located on top of the transmission. Perhaps you changed the wrong sensor? If you have replaced the actual speed sensor, I suspect that the unit that the speed sensor 'reads' is faulty down inside the transmission. This could be due to several things. A broken tooth on the unit that the sensor reads will compromise the signal. You may want to pull the sensor out and investigate inside the transmission.
Customer: replied 1 year ago.
There are only two speed sensors on this trans. One near the bell housing and one at the rear of the trans. Both on the drivers side. No sensors on the top of the trans. I checked the voltage generated by the output shaft speed sensor and it produces 6 volt a/c at 40 mph. When I disconnect the wheel speed sensors I get no speed signal at all on my scanner or the speedo. I also checked the trans and no obvious signs of a broken or missing tooth. I really lost on this one.
Expert:  Toyota Service replied 1 year ago.

Yu can get a P 0500 if wire to the ECM is faulty, or, if the speedometer is bad too