How is it the Check Engine light is not on with the missing converter? The rear, or downstream oxygen sensor is only there to monitor its efficiency. The front one switches between rich and lean a couple of times per second. The rear one will switch maybe once or twice per minute when the converter is doing its job. If you put the rear sensor in line with the front one one, it will switch at the same rate. That's how the computer knows it's not changing the composition of the exhaust gases. Once it knows it can't rely on the oxygen sensors' readings, it will not run some self-tests. Other problems which could start out as being very minor will not be detected. Normally the Check Engine light will be on all the time so you'll never know when another problem is detected.
Fault codes never say to replace parts. They only indicate the circuit or system that needs further diagnosis. The sensor referenced by the code is actually the cause of the problem about half of the time. There can also be cut wires, corroded splices and connector terminals, and things like that. Given you have three codes for three different things, start by looking for something they have in common. Typically that is a 5.0 volt supply wire but it can be a ground return wire too.
Tuesday, March 5th, 2013 AT 7:30 PM