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?

Johnboy

[dmcmahon]

I am having the same/similar problem. My '04 Sienna LE AWD's CE and VSC light went on and then was reset. After a week or so they came on again and went off on their on. Finally ithey returned and stayed on. The delear ran the system check got codes P0420 and P0430, "Catalytic converter below threshold bank 1 and 2". They performed and ECM update for the associated parameters but the CE light returned the next day. My wife's '02 Highlander has a similar problem every time she gets her oil changed (at the dealer). This has been always due to a loose vacuum hose and/or not properly tightening the gas cap (should hear 3 clicks). The vacuum hose probelm is due to a short hose that should have simply been made longer. I am not ready yet to pull the trigger on a new CAT converter. It could be a vacuum hose or and Oxy sensor. More investigation is necessary.

Stay tuned,
-Donn