My 00 4Runner keeps throwing the PO151 code. I have cleaned the MAF, installed new plugs & wires and am still getting the code. From what I have searched...it appears that I should replace the MAF now...or possibly the AF (which I don't know where it is?). I just have a quick question.....Would a bad MAF cause the 4R to run extremely crappy on the first start of the day? It surges and sounds like it's gonna stall when you put it in gear until it gets warmed up......just want to confirm that this sounds like the problem before I drop a $C-note on the MAF.
THANKS!!!

 

Can't remember my code (had something to do w/ running lean) but first did the A/F sensor (upfront O2 sensor for cali-spec trucks) and my code wouldn't go away. Cleaned the MAF and still the code. Replaced my MAF, code disappeared.

As far as how the truck ran, I couldn't tell a difference before and after the A/F and MAF swaps. In my head, the truck ran better w/ the codes.

 

ohio4runner, I am assuming you meant code P0171 because it is impossible to have code P0151 "O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)" on a 00 4Runner since there is no sensor bank 2 on these V6 motors.

If you have already cleaned the MAF and the code returned, then yes, it's time to replace it. If that also fails to keep the code from coming back then you'll need to replace the front A/F (O2) sensor. Be sure to pull the neg batt terminal to reset your codes after each repair attempt.