I 'm getting codes P0325, P0330 & P0171 on my 2000 Lexus ES300 with 131K miles. Car will not go into overdrive 50% of the time. Transmission was checked out and serviced & was told overdrive issue is due to bad knock sensors. I talked to many repair shops, none of them know if changing knock sensors will fix my overdrive problem. Any advice?

 

My advice, don't use bold italics.

Yes certain codes such as knock sensor error can cause the computer to prevent O/D from engaging.

 

P0325 and P0330 are knock sensor codes for both cylinder banks. The ECU is not getting any signal from the sensors, therefore they should be replaced. When these codes are present the ECU will block out overdrive, so replacing the knock sensors will more than likely fix your overdrive problem. Any reputable shop with Lexus experience should be aware of this.

P0171 is a lean code. If your ES is anything like mine under the hood, check all the vacuum hoses and any other rubber connector going to the throttle body as they tend to get very brittle and crack, causing vacuum leaks resulting in a lean condition.