1996 Chevy Blazer check engine light on

P0440 is an OBD-II generic code that the engine control module (ECM) has detected a leak in the fuel tank vapor system or a vapor pressure sensor has malfunctioned.

It might be open door?

TYPE: OBD & your codes

OBD PO440

OBD PO302

etc & do some studying (learning)

http://repairpal.com/OBD-II-Code-P0440 Check this site out.

Check engine light comes on when the computer detects a problem. Your car is OBD II and you need an OBD II scanner to retrieve the code(s). The code(s) will tell you the problem and from there you can figure out the proper fix. Some auto parts stores will retrieve the codes for free,

Check engine light comes on when the computer detects a problem. You will need to have the code(s) retrieved using an OBD II scanner. Some auto parts stores still do this. Once the code(s) have been retrieved you can figure out what's wrong and how to fix it.

If your talking about the Check engine light. You will need a CHEVROLET OBD I code reader. the auto makers used their own style of ports and language until OBD II in 1996. The code reader can be purchased at most auto parts stores and it isn't very expensive.

Use the OBD-II scanner for 1996 and up vehicles to clear codes and shut the service engine soon light off if set. I would read the codes before doing this, though, to get a clue as to what is tripping the ECM's light in the first place.

One can get a scanner for under $100 from Sears or Walmart or get the local Autozone or Advance Auto Parts to do it for free, if they do that in your area.

you need an obd2 code reader

i have 2003 trailblazer ltz 153 000 mileage i have code po440 .i changed gas cap and turned off the chech engine light... i made 300 miles and it was good and today morning i drove a mile and light turned on ..... what do i have to fix ...thanks