[Sabster]

Hello everyone, sorry that my first post isn't a normal Hello post but I have a problem I can't seem to solve. I hope someone has seen this problem before and can point me in the correct direction.

I recently purchased a 2002 Mustang GT and to my dismay the Check Engine Light has come on and I can't seem to keep it off.

I ran a check on the error code it was throwing and I keep getting this error code P0156.
Which is Downstream Heated Oxygen Sensor circuit fault - Bank No. 2.
Or O2 Sensor Bank 2 Sensor 2.

I have replaced that Sensor cleared the code and the light came back on again. After checking the codes again, still the same error. P0156.

I originally thought that perhaps I replaced the wrong O2 sensor, I replaced the driver side, post CAT. So once it came back on I replaced the Passenger side thinking that maybe I replaced the wrong one.

Being that both these sensors are new, I am still getting this P0156.
I can clear the code and drive the car a couple of times before it comes back on and I am at a loss of what may be causing this.

Can anyone suggest where I should look next?

This is starting to drive me crazy, there is nothing worse then having a problem with a new car, well, new used car.
Thanks for your help!

[FunkyBoss]

Maybe your cats are bad. Have you checked the harness for burns or breaks?

[Sabster]

From what I could see the harness looked OK, I did see a 'Zip Tie' on the passenger side harness which made me think Hmm... but other then that they looked ok.
If it’s true and the cat(‘s) are bad wouldn’t a MIL eliminator take care of the check engine light problem? If so there is one possible route I can take. I do know that it passes emissions when the light is off. The car runs great, so I am at a loss. Here is another question that may help me find the problem. Is there a way to use a laptop to read the errors from the computer? I hate having to run to the auto parts store to use theirs each time. The last question is this, I was thinking about getting under there and checking the voltage it’s sending back when the car is running, I know it’s supposed to be under 1 volt, I am wondering if anyone has tried this before.

[blue_08]

Since you already changed the your o2 sensor it could be caused by the moisture in the number three cylinder sparkplug well. The guy I spoke with used to work at a Isuzu dealership when I had a problem with the code P0156 in my Isuzu oxygen sensor and told him what it was doing he said it was either the plug, the wire or moisture in the plug well making it arc and spark from the end of the plug wire. I blew it out with compressed air and it fixed the problem. It was when the remnants of some hurricane had come thru and the truck had sat in a pouring rain for four days...I assume the water leaked down through the cowl between the windshield and the hood onto the top of the motor and ended up in the number 3 plug...

Well, I have driven it since my last post and have not had a recurrence of this problem. Good luck!!!

[Sabster]

I'll check that out too but from what I can tell everything is sealed. This weekend I plan on seeing if there is a problem with the connection to the sensor, make sure it's getting the right voltage and see what it's putting out. I am not reading any detected misfires or rich / lean readings. It's just a fault, I am also going to swap the leads from both bank one and bank two and see if I can get the error to move to the other side. I'll keep this updated with my progress.