2001 Sienna check engine light on.

[Johnboy048]

Back last summer the Check engine light (M.I.L.?) came on and I went to a repair shop near me and a scan showed P0174 and P0171, lean fuel mixture bank 1 and 2. Shop installed 2 oxy sensors and the light went out but came back on in 2 days. It seems like the codes were the same. I can't remember. I installed a new gas cap and this was of no help. Finally gave up. I was out almost $600 by this time. Car was running fine, so I kept driving it and the other day when I unhooked the battery to clean a corroded terminal, the car ran rough for several hours afterward. Took it to the Toyota dealer and now got code P1135. Replaced another oxy sensor and cleaned MAP sensor. $335. Light came back on after several miles of driving. Went back to dealer and code was P0420, cat converter. He wants well over $1000 for installing a new Toyota brand converter. No guarantee that light will not come right back on. I said the heck with it and left. Car has 107K miles on it and runs good. Can I continue to ignore that darn light? I feel like I am caught in a trap with this car. I have never had this problem with any Ford or Dodge and I drove them to 150K. If it has to be changed, what about a cat converter from Autozone or O'Reilly and a change by a muffler shop?

[mral1515]

It appears you may have a few problems with your vehicle. In most case the codes P0171 and P0174 are for the mas air flow sensor.

The code P1135 is for an air fuel ratio sensor ( same as an O sensor ).

Please keep in mind it is very difficult to diagnose a vehicle over the internet.

As far as the P0420 this could have possibly been caused by original code for the mass air flow sensor. When those sensors are acting up they can really put your catalytic converter through the ringer. You can replace the converter through an aftermarket source however I would recommend that you do it with the same company. For example let the company that installs the converter get the part also. That way they can warranty the part they put on. Hope this helps. Please let us know how it works for you.