Help W/2003 Mustang Gt

Discussion in '1996 - 2004 SN95 Mustang -General/Talk-' started by Michaelp, Aug 3, 2013.

  1. Hi I'm new in these page but I need some help please let know what you guys think I have a 2003 mustang and it won't pass the smog on CA because the scan read that it's the o2 sensor buy I already bought all 4 new from O'rallys an even then the service engine light it's on even if u drive it for a lot of miles does any one knows what might be wrong? Any ideas thanks
  2. You need to clear the code. Unhook the battery for a few hours.
    #2 Nightfire, Aug 3, 2013
    Last edited: Aug 3, 2013
  3. I did but after driving it for few miles the light come on again same code its it possible that the previous owner might of plug in a scanner For mods?
  4. What code are you getting? Do you have cats on the car? Are they high flow/aftermarket?
  5. I do I have the stock catts and the code I am getting said o2 sensor bank 1 an 2 or something like that I replace all four because I was getting the same code every time
  6. Yes, but what is the specific code? The are hundreds of codes and many of them are closely related, plus many of the codes involve the O2 sensors because it is such an important system.

    Still blind, I would suggest tracing some of the wiring to make sure it is in good condition. There is also a heater circuit for each O2 sensor. It would be good to confirm they are getting that signal as well. You can monitor the O2 sensors using a digital multimeter. If the computer is in closed loop (most of the time it is), then you'll see the voltage of the signal wire swing quickly between ~0.8v and ~0.2v. That's normal. Then, at WOT (open loop), it will probably run 0.8-0.9v. This is for the fronts.