I have a 2002 prius with 197k, that I've had for about 1 year. I replaced a cell in the traction battery about 6 months ago, and got the p3191 error when starting back up after the rebuild. I disconnected the 12v battery, and the code went away. After driving for about 15 minutes the car was acting normally again. This week I did a full rebuild with 38 cells from a 2011 prius. I got the p3191 code again. I disconnected the 12v battery for a while, reconnected, and the code went away. I drove about 20 miles, no problem. The next morning the code was back, and now I can't make it go away. Having just spent almost $2000 to rebuild this thing, I am tapped out. Any ideas? Other issues- the AC runs for 5 minutes and then stops working (ac button blinks, air stops being cold). This was a problem with the old battery, and still is with the rebuilt battery.
the p3191 code is for the engine failed to start. i would take off the air filter and check down in your intake and see if there is oil pooled up in there. I got that code, cleaned out the oil and all is well.
The prius uses the atkinson cycle engine which is different than other engines. therefore unfortunately oil gets pulled in past the throttle body and lays down inside the intake manifold and can pool up and what happens is when the prius engine starts at 1200 rpm spun by MG1, the engine sounds like it but actually has not for about a couple seconds began firing the spark plugs to start and what happens is that oil laying in the manifold gets sucked into the cylinders and can be enough sometimes to coat the spark plugs and the plugs wont be able to deliver a spark once the computer tells the car to send spark to the engine, the result is the code that your getting. you can take off the throttle body or leave it on (i left mine on). just take off the stuff before the throttle body(air filter box) and by hand open the throttle plate. and look down in there, if there is oil pooled in there, get a long screwdriver or a stiff coat hanger(coat hanger is better) and a rag (DO NOT USE A PAPER TOWEL) use something like a shop rag, or t-shirt material. and get that down in past the throttle plate, once its down in there move it around and get as much of the oil as you can. than pull it back out. now get another clean rag set up but this time to go in there and spray some brakeclean or carb cleaner in there than go in there with the rag. do as you did before. once your done pull the rag back out and put everything back together. then fire it up. if it still wont start, your mass air flow sensor may be shot. hope this helps
pft, I am having a similar problem as you 3 years later. I rebuilt the battery and reinstalled. I disconnected the 12v battery to clear the codes. Now I am getting a P3191 and cannot figure it out. Did you have success following scotman27's advice? Or what did you do? Thanks!
