We have to recommend checking the Oxygen Sensor on your Chevy Blazer. If in
fact the trouble code is accurate, you'll have to find out why the engine is
producing low carbon monoxide (CO) and triggering a lean flag or lean
trouble code. You'll need to do a fuel injection "feedback" test. You'll
need to check and make sure the oxygen sensor is working properly and the
engine control computer (ECC) is sending the right amount of fuel to the
combustion chambers.
The "feedback test" is conducted using propane. Propane is added to the air
intake system while measuring voltage output from the oxygen sensor as the
engine is running at idle; you should see an increase in voltage up to .90
volts, and the injector pulse width should immediately decrease. If this
does not happen, we know we have a feedback problem. From there you'll need
to find out which part of the feedback system is at fault; the oxygen
sensor, the fuel injector, the engine control computer, or the wiring
between these components.
At the end of the feedback test it will be know whether the low CO fault is
electronic or mechanical, and the technician can further diagnose the fault.
