he is definitely handing you a line. i had a lift on a chevy and never had that problem. i believe the o2 sensors are used to monitor the oxygen content in the exhaust after combustion occurs in the engine. this sensor allows the computer to regulate what the oxygen/fuel ratio is going into the motor. the o2 sensor may be the cause of the service engine soon light, but for 11k he can replace that and it should fix the problem. if the sensor is detecting too much air from the lift, then the exhaust system has a leak or hole in it which he would definitely need to repair/replace. i wouldn't even consider purchasing the truck until he fixed that issue. assuming he does, and it's a 4x4 (why else would it have big tires and a lift) with even the small v8 (4.7 vs 5.9) that is a good price. almost too good if you ask me because that is less than trade-in (kbb.com). i would be very cautious and even ask to test drive it to another dodge dealer and have their service guys check it out. tell him, you will foot the bill if you don't buy, if you do buy then he has to absorb it. this may sound like a waste of money but trust me when i tell you that his "warranty" won't even begin to cover the cost involved if that light is from something else. (computers can be upwards $1500 easy in newer model trucks.) it'll be the best $50-$100 you ever spent. if he won't agree he is telling you everything you need to know, i say walk away...
note: don't let him tell you he can't do that either. you'd be surprised what a dealer will let you do if it means selling that vehicle. don't budge.
hth!
note: don't let him tell you he can't do that either. you'd be surprised what a dealer will let you do if it means selling that vehicle. don't budge.
hth!