[Boady]

Forgive the long post but I want to make sure I include everything to help trouble shoot this.

I have a 2002 Grand Cherokee Overland. A couple of months ago I had a slow leak in a power steering line that I trouble shot to the line connecting to the pump. The line had play at the fitting. The jeep already had an appointment at the dealership to have the oil changed so I asked my wife to have them look at the fitting and tell me if there was an O-ring under it I could replace. Well, they charged me the full diagnostic fee to find the hose I knew about. They told her the pump and the line had to be replaced as a set. Then the mechanic got attitude towards my wife when she did not let him replace them.

The next day the check engine light came on. Using the "always check the last thing you messed with" technique I checked the oil and filter. The jeep was over serviced with oil by about 1 quart. I am a mechanic (previously marine diesels and now helicopters.). I was buying the power steering line at the dealership so I stopped in to ask if over servicing would give any codes. the manager got very hostile and said you could fill the thing to the top and not hurt it. Note: The Jeep has a warning on the dip stick telling you "DO NOT OVER FILL".

I checked the codes and one of them indicated a bad gas cap. No problem, bought it and replaced it. The code did not go away. Later I was walking by the left side of the jeep and heard what sounded like an exhaust leak. I crawled under the vehicle and found the source of the sound was an open line. Because of it's position it's obvouis it was pulled off by someone. It was wedged between two other lines and when I relieved the pressure it snapped back to it's original position at the coupling. I reconnected the hose and the one code is now cleared.

The codes I have left are:

P0051 02 Sensor Heater Control Circuit Low (Bank 2 Sensor 1)

P0152 O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)

P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)

Could overservicing the oil cause this? I don't see how but I've been wrong before.

My thinking is that it's odd that two sensors would go out at once. Is it possible that one is bad and throwing the entire system off?

[Boady]

I wanted to post a follow up just in case someone else is having similar codes etc.

I started by checking all the oxygen sensor connections and found one that was partially disconnected. It turned out to be the bank 2 sensor 1 oxygen sensor. I plugged it in and erased the codes. i drove for about 5 miles and the check engine light came on again. I checked the codes again. I got P0051 and P0155. Partial success. Erased the codes again and drove home. This time only P0051. Both Codes pointed to the Bank 2 sensor 1 O2 sensor. I replaced it and the light is gone.

i spoke with quite a few people who have said when one goes out you may as well change them all out. The reasoning is that they have the same expected service life. They were installed at the same time originally. When you change one it's just a matter of time before another one fails. If you can afford it the cost it's better to climb under your rig once and change them all then do it randomly four times.

Hope this helped.

BTW I am at a loss as to what to do about the Jeep dealer. It was a few months ago that they worked on my Jeep. The over servicing is no big deal it happens. The intentionally disconnecting an emissions hose and O2 sensor is what bothers me. I would not expect that from a dealership.