My 2004 Corolla has an engine warning light on, the code is P0171, so I brought my car to NORTHWEST TOYOTA in Brampton to repair on Feb 4, 2009. After engine check (labor rate $103), I was told by a confident service consultant in front desk Raymond Rajgopaul that my car had a minor and common problem. I have accepted estimation and second day the technician has replaced thermostat and new battery for my car. I was told my car was completely fixed and asked me to pay for around $450. When I picked up my car in parking lot after payment, I used my ODB-II meter to check and still found some warning info. I showed what I got to anther service consultant in front desk, because Raymond was off when I picked up my car, but he said the technician had forgot to clean error history and my car was absolutely fixed and he told me If light come on in one or 2 weeks, free charge to fix my car. Unfortunately, second morning, my engine light come on again and I read same code P0171.It is very strange thing that my sample meter can find error code, but Toyota diagnose equipment can’t find. I think Technician must have made mistake to replace wrong part or didn’t diagnose clearly at all. Later Monday morning (Feb 8, 2009), I sent back my car to Toyota, but I was told anther different part (PT# TO28226-28051; intake gasket) need to be replaced. I wondered even new part will be put in my car it is still in trouble. But Raymond said this time my car would be fixed for sure, only charge me about $100 for labor. I thought it is unreasonable to double pay for same job and I doubt if this technician found real problem for first experience of Toyota service and I wanted to talk with the technician face to face, but I was refused by Raymond. After I offered to see service manager, I got a note read "NO Charge for repair code P0171 to customer”, but I have to wait until a back-order part coming. Raymond told me my car can be drive during waiting, but I worried, so my car keeps in my garage now. Today, 10 days is over, but I still wait for the part and parts manager Mike Agius said some customers have already been waiting for 1 or 2 month because it is a back-order part. Whatever I don’t understand what’s a back-order part. My question is whether I can request a senior Toyota technician appointed by Toyota head office to answer me if they have a correct diagnose this time and if this is safety to my car to drive under this condition. If not, who will be responsible to kill my car? I hope some authorized person from Toyota Canada can tell me if it is a true Toyota policy about this model Corolla to let a car owner drive a defective car to wait for this back-order part and nobody know when it will be in. Why this part will take too long to order. If not, please tell me how to solve my problem ASAP in avoiding to ruining Toyota reputation in my mind. So far, my family has two Toyota cars (one 2000 Camry; one 2004 Corolla), because we used to trust Toyota’s products. I just bought this used car three month ago, because my 1999 Corolla had an accident on Sept 1st, 2008 and was write off. I don’t know if my new Corolla has what kind of warranty or nothing.