I have a 1996 Geo Tracker (a Suzuki at heart) that I keep getting the same check engine light code P1451.  This seems to be a top secret code because no one is willing to talk about what it means, where the problem can be located, how to troubleshoot it, and what components may be involved in fixing it.  I get good milage (35mpg), and it runs great, but the stupid light keeps coming on no matter how many times I reset it with my Acutron scan tool.  I can't see paying Chevy $$$ to plug in their scan tool and fix a minor problem that I may be able to fix.  Has anyone had the same problem? If so, what was the cause and how did you fix it?  My Haynes manual is not too helpful.  And I can't pass an emissions test if the light keeps coming on.  Any new information would be greatly appreciated by this frustrated mechanic.

You need to find a schematic or workshop manual and determine where the barometric sensor is. It gives an output of 0-5V when it is working properly. You may just have a bad connection or a vacuum leak. These sensors are usually quite reliable.

Thanks for your reply.  So does Chevy still call it a baro sensor or did they pull a fast one and name it something else?  Usually when I reset the light, it stays off for 25 to 100 miles then just before it comes on again, I get a short period of mild rough idle, and the light comes on again within a few miles.  After that, the idle settles down and I get a little less milage.  My Actron scan tool always shows the code as a pendinf failure.  I will look further--it is 12 years old and has 160,000 miles, but it is a great car.  Again, thanks for breaking the silence.
Tailrotor

I don't have any Geo information. I expect that they would use something very similar to the MAP (Manifold Absolute Pressure) sensor on an 8V.