98 Mustang 3.8 check engine light?

It has been checked ( codes ) by the part store and they come up with nothing. A friend had a code reader and he said nothing comes up but maybe a possible lean condition from the right rear o2 sensor. This was replaced but the light comes back on. The car seems to start and run fine but with the light on it can't be tested for state emissions test.

I tried to do a reset by disconnecting the battery then running for 100 miles but the light came back on.

Any ideas?

Unplug the light until the emisson test is done?

Actually this could be a couple of things:
Battery needs to be serviced
Solid State PCM Error
Electrical Connection is loose

Ok I took the car to a different auto store and they had a code P1151 come up which they said was manufacter controlled fuel and air metering.

Is this a sensor that I could pull and clean? Or is it something more that I would have to take to a dealer.


TXS.

You are running lean and wouldn't pass emissions if you did unplug the light :(

Things I could think of:
Faulty or Damaged O2 harness
Poor Engine/Clyinder Compression
Faulty or Damaged O2 circuts
Faulty or Damaged PCM
Dirty or Clogged Airfilter
Improper Fuel Pressure or Cam Timing
Faulty or Damaged fuel injectors
Low Pressure in return lines
Air leaks after the Mass Air Flow Sensor
Intake Vacuum Leaks
Oil Cap or Oil Stick not secure
Stuck EGR valve
Leaking diaphragm or EVR
Exhaust leaks before or near the O2S






I would look at the O2 Sensors, Vaccum Hose and leaks first.

Whelp it was the DPFE Differential pressure feedback egr sensor.
$67.00 @ NAPA and all is well.