P0770 Lexus GS 300 , 2000

Question

2000 Lexus GS 300: Getting a code of P0770 E Shift Malfunction. Late shift from 1st to 2nd. After that I have no issue. Also on the 1st gear it is also pretty good except shifting late.

I had the chance to flush the transmission fluid and replaced filter. Fluid was redish purple and tiny metal on the 3 magnets which is understandable for a 168k mileage. 5 Solenoid that is accessable but I was not sure which one is the cause of the problem or which one to check. The 5 Solenoid are the following: Linear Soleoid Valve SLT, Linear Solenoid Valve SLU, Linear Solenoid Valve SLN, Shift Solenoid Valve No.3 (83), Shift Solenoid Valve No.1(S1). I know there's two more but I believe it's inside and those two are the following: Shift Solenoid Valve No. 2 (S2) and Shift Solenoid Valve No.4(S4). Can someone please tell me which is the Solenoid that I need to check including the wires. I hope the Solenoid that I need to replace is only Linear Solenoid SLU or even better just a loose wire. My AC also started blowing hot air when my transmission started acting up. I'm not sure if it's just a coincidence. Or it could be an ECU issue.

Answer 1

The ECM uses the Mass air flow sensor and the throttle position sensor to engage the torque converter. 

I would try to clean the mass air flow sensor with mass air flow sensor cleaners and clean the throttle body before anything else 

also see diagnostic procedures and picture below