A faulty EGR valve can cause a 98 Chevy to fail a smog test. The oxygen sensors should also be tested as they can also cause a 98 Chevy to fail a smog test.
DTC - 44 Oxygen sensor error (lean condition indicated)
How do you change oxygen sensor on a 2006 Chevy aveo?"
How do you unplug an oxygen sensor on a 2003 Chevy Cavalier
where is the O2 sensor on a 2002 chevy trailblazer
The Exhaust Manifold Oxygen Sensor needs to be replaced.
where is the oxygen sensor in a 1995 gmc jimmy
On the muffler
somewhere
The sensor is located in the rear exhaust manifold.
in the exhaust system
on the muffler
Just unplug the electrical connector and then unscrew the oxygen sensor out of the exhaust pipe.