Local auto parts ran a diagnostic scan on my chevy cheyenne pick up found a code that stated vacum leak or bad evap sensor or hose cracked or leaking where is is this located on my chevy 5.3 vortec engine

take to autozone and have them run a scan. they will give a print out of code and possible replacement parts. remember they do not repair cars they sell parts.

Evap system has many parts , cannister,vent and purge valves ,fuel tank and cap, first is the fuel cap on and is the seal in good shape. You will need to inspect all vauum hoses that leave the cannister if all ok then get the valve and solenoid tested for stuck open

you PCM has spot a problem in the engine control system.you have bad sensor or EVAP leak or cylinder misfire.any auto parts store will code scan vechicle see what cause check engine light to flash on.they will code scan vechicle free go by auto zone.

go to auto parts store so they can get the trouble code , that is causeing light to come on. it could be a vacum leak or a bad o2 sensor

code p 0442 refers to evaporative emissions(EVAP) system---small leak detected ===causes ---hose connections ---intake leak---EVAP canister---EVAP cannister purge valve
it also refers to mechanical fault --hose connections --EVAP pressure sensor

Check for a loose hose on the purge valve

HI. This will require you to have the engine CPU scanned for trouble code's. This can only be administered with the assistance of a diagnostic computer scan tool. You can purchase this tool at your local auto parts store, or you can just have the scan ran at your local auto zone parts store, free of charge. Once the diagnostic scan is administered, you will be able to isolate the issues that have caused the check engine light to illuminate.

This scan tool will display a print out code and the location of the issue, on the engine, as well. There are Many issues that will cause the engine light to illuminate, but the most common cause will be a failed monitoring sensor, or sensor harness failure(separated power wire, or ground).

Once you have the codes, kindly return to the site, and post them here. We will be able to assist with more accuracy, once the codes are posted.

Thanks..

Easier said then done without professional tools

However, I'll start you will some theory, then the shop manual procedures followed by some "common" problems

Theory:
Evaporative leak detection strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. Powertrain Control Module (PCM) monitors vacuum level by means of fuel tank vacuum sensor input. At a predetermined time, EVAP purge solenoid and EVAP vent solenoid are turned on. This allows engine vacuum to draw a small vacuum on entire EVAP system. Whenever a sufficient vacuum level cannot be achieved, a large leak or faulty EVAP purge solenoid is indicated.

Conditions for setting this DTC are as follows:
No TP sensor, ODM, IAT sensor, or MAP sensor DTCs present.
Start-up ECT 40-86°F (4-30°C).
Start-up ECT not greater than 14°F (8°C) greater than start-up IAT.
Start-up IAT not greater than 4°F (2°C) of start-up ECT.
Fuel tank level is 15-85 percent.
BARO is greater than 75 kPa.
Vehicle has been driven at least 11 miles.
EVAP system is unable to achieve or maintain vacuum during diagnostic test.

Diagnostic Procedures
1.) Perform On-Board Diagnostic (OBD) system check.
After performing OBD system check, go to next step.

2.) Check if DTC P1665 or P1676 is also set. If any of DTCs is present, diagnose affected DTCs. If DTCs are not present, go to next step.

3.) Turn ignition off. Remove fuel filler cap. Turn ignition on. Using scan tool, observe fuel tank pressure. If fuel tank pressure is zero in. H2O, go to next step. If fuel tank pressure in not zero in. H2O, diagnose evaporative system.

4.) Replace fuel filler cap. Using scan tool, capture FAILURE RECORD data for DTC P0440 and clear DTC. Command EVAP vent solenoid on. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP service port. Pressurize EVAP system using diagnostic station. Monitor pressure on EVAP pressure gauge on diagnostic station. If pressure is 5 in. H2O, go to next step. If pressure is not 5 in. H2O, go to step 6.

5.) Maintain EVAP pressure at 5 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure reading on scan tool is 5 in. H2O, go to step 8. If reading is not 5 in. H2O, go to next step.

6.) Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Block canister fitting for fuel tank pressure line. Connect a hand-held vacuum pump to canister fitting for EVAP purge line. Ensure that EVAP vent solenoid is still commanded on. Apply vacuum to EVAP canister. If vacuum can be maintained at 5 in. Hg, go to step 11. If vacuum cannot be maintained at 5 in. Hg, go to step 10.

7.) Check for restriction in fuel tank vapor line or EVAP purge line. Repair as necessary. After repairs, go to step 16. If restriction is not found, diagnose EVAP system.

8.) Disconnect vacuum source line at EVAP purge solenoid and plug vacuum source fitting on solenoid. Using scan tool's output tests function, select and activate SYSTEM PERF. Pressurize EVAP system to 5 in H2O. Observe EVAP pressure gauge on diagnostic station while removing plug from EVAP purge solenoid vacuum source fitting. If EVAP pressure decreases to zero in. H2O within 15 seconds while system performance is activated, go to next step. If EVAP pressure does not decrease to zero in. H2O within 15 seconds, go to step 13.

9.) Install vacuum gauge on EVAP diagnostic station to vacuum source line. Start and operate engine to greater than 2000 RPM. Observe source vacuum level. If vacuum level is greater than -15 in. Hg, If vacuum level is not greater than -15 in. Hg, go to step 14.

10.) Check for disconnected or damaged vent hose. Check for damaged EVAP canister. Repair as necessary. After repairs, go to step 16. If no problems are found, go to next step.

11.) Check for faulty or missing fuel filler cap. Check for disconnected or leaking fuel tank vapor line. Check for disconnected or damaged EVAP purge line. If problem is found, repair as necessary. After repairs, go to step 16. If no problems are found, go to next step.

12.) Using scan tool, command EVAP vent solenoid on. Continuously attempt to pressurize the EVAP system by leaving the EVAP diagnostic station control knob in the pressurized position. Using the Ultrasonic Leak Detector (J-41416), locate and repair leak in EVAP system. After repairs, go to step 16.

13.) Replace EVAP purge solenoid. After replacing solenoid, go to step 16.

14.) Check for carbon release into the EVAP system. Repair as necessary. After repairs, go to step 16.

15.) Replace EVAP vent solenoid. After replacing solenoid, go to next step.

15.) Turn ignition on. Using scan tool, command EVAP vent solenoid on. Using EVAP diagnostic station, pressurize EVAP system to 15 in. H2O. Move rotary switch in diagnostic station to HOLD and observe EVAP pressure gauge. If EVAP pressure decreases to less than 10 in. Hg within 2 minutes, repeat step 3. If EVAP pressure does not decrease, system is okay.

Diagnostic Aids
Check for the following:
Cracked or punctured EVAP canister.
Damaged or disconnected source vacuum line, EVAP purge line, vent hose, for fuel tank vapor line.
Poor connection at PCM.
Inspect harness connectors for backed-out terminals, improper mating, broken lock, damaged terminals, or poor wire connection.
Check for intermittent in circuit.
Check for kinked, pinched or plugged vacuum lines to EVAP purge or fuel tank vapor line. Also check for restrictions.
Faulty or damaged evaporative canister.

If you have an EVAP leak, you will get the following codes:

1. P0442 evap emission control system leak (small).
2. P0455 evap emission control system leak (large).

If these codes come up, you need to trace the leak. The most common place for the systems to leak besides the gas cap is at the service port under the hood, the hoses at the purge solenoid, and the hoses around the fuel tank. Check all your EVAP hoses from under the hood , all the way back to the gas tank. You can repair a split hose easily. Buy some 14.5mm EVAP hose at the auto parts store. Just cut the split or cracked section out and attach the new hose.
I can only say that u must fix the code issue and light to pass state emission test, if u reset the light they will know, the system will tell the tester that the system is not ready, this will cause a fail.

I am not going to lie, I came across this in another forum a while back and I would love to retype it and interpret it here but it is too much. I looked at it and verified that the information here is information that could be found through my scan tools so here it is!

P0440
The fuel tank pressure is atmospheric pressure after the vehicle is driven for 20 min (2 trip detection logic).

Possible Problems
Fuel tank cap incorrectly installed <= Most common
Fuel tank cap cracked or damaged (Toyota part only)
Bad vapor pressure sensor/circuit
Vacuum hose cracked, holed, blocked, damaged or disconnected 
Hose or tube cracked, holed, damaged, or loose
Fuel tank/filler neck cracked, holed, or damaged
Charcoal canister cracked, holed, or damaged (collision)

In above description, check hoses between vapor pressur sensor and VSV for vapor pressure sensor and charcoal canister. Also, hose between charcoal canister and fuel tank.