My check engine light is on and a diagnosic scan showed up with P0440 first and then when redone a couple of months later, the scan showed up P0440 and P1665 (O2 sensor). Would the O2 sensor cause the P0440 light to pop up to, or is this a seperate problem?

Type: OBD & your codes

OBD PO 440
OBD PO128

Codes have nothing to do with installing parts

Codes are System Faults only

Codes are used to diagnose a system & component
test to find a problem

http://www.engineobd2codes.com/p0440_honda-pilot.html

have you tried removing the battery terminal/disconnecting the battery for couple of minutes so the computer can reset.

The (air bag) SRS System has to be diagnosed to answer that

Why was that not done when the check light issue was resolved

Your lucky you had no accidents as the air bag is most likely
turned off,so why have you waited 9 months

You clearly never want to use that repair shop again

This could be caused by a bunch of thing's , fuel system , engine sensors , ignition system , PCM etc.... Testing is the way to eliminate guessing . Viewing scan data is the best way to diagnose these type problems .
047 Engine Hard to Start or No Start Scan Data for Ignition
048 Engine Hard to Start or No Start Scan Data for Starting Problems
002 Fuel System Tests Start Here

Your best bet take it to a qualified repair shop .

Diagnostib Test Code (DTC) P0440 is defined by SAE J2012 simply as "Evaporative Emission System".

This code is what I call a "catch-all" code for the evap system. This is the code that sets when all the other EVAP codes do not apply and there is a malfunction detected in the EVAP system.

It is not really hard to diagnose this code if you have the correct equipment and understand how the EVAP system operates.

How DTC P0440 sets:

The system is tested when there are no electrical problems with the Purge Control Solenoid Valve (PCSV) or Canister Vent Solenoid Valve (CVSV) circuits and the Fuel Tank Pressure (FTP) sensor voltage is within the operating parameters. The Powertrain Control Module (PCM) commands the CVSV to close and the PCSV to open and apply vacuum. It then looks for a change in the FTP voltage to indicate that there is a vacuum being drawn on the fuel tank. If there is no change, DTC P0440 sets.
If there is a change in FTP voltage, the PCM draws the vacuum to a predetermined set point and closes the PCSV (leaving the CVSV also closed) and looks for decay in the vacuum in the tank as evidenced by the FTP voltage. If the predetermined set point cannot be reached, DTC P0440 sets. If the set point is reached and the decay is faster than allowed over a predetermined time period, DTC P0440 sets.

It should also be noted that the monitor for this code is a "type B" DTC, meaning that it must fail on two successive drive cycles before it will turn the check engine light on. So, if it fails on the current drive cycle, then the conditions for running the monitor are not met on the next drive cycle, the code will not set on the second or third drive cycles. All conditions must be met and the monitor must fail two drive cycles in a row. This explains why it may take a week or two before the check engine light comes back on.

This code is very easy to diagnose using a scan tool that is capable of performing "purge and seal" tests and graphing the FTP voltage over time. The technician can actually "see" the vacuum being drawn on the fuel tank and the vacuum decay by doing it this way. Repairs can be verified this way without having to drive the vehicle several times to get the EVAP monitor to run.

By running the evap purge/seal function on the scan tool and using hose clamping pliers, different parts of the system can be checked by clamping off the hoses that connect the components and watching the FTP voltage graph. If there is no change in the FTP voltage when the system is commanded to purge, a vaccum gauge should be used to verify that the purge solenoid is actually working and that vacuum is being applied to the rear of the vehicle There could be leaks in the line between the purge solenoid and the canister.

For an example of how this works:

Possible rust holes in the filler neck and/or a defective fuel cap can be determined if there is no change in the FTP sensor voltage or rapid decay upon the initial test that goes away when the filler tube hose is clamped off between the filler tube and the fuel tank. A sticking CVSV can be determined in the same fashion by clamping off the hose between the charcoal canister and the CVSV.

Holes in the hoses themselves can also be diagnosed the same way by disconnecting them from the vacuum source end and plugging the source tube. Example, remove the vent hose from the canister and plug the hole in the canister. If the problem goes away, it is either the hose leaking or the CVSV leaking. So, reconnecting the hose to the canister and disconnecting it from the CVSV and plugging the end of the hose will tell you if it is the hose or a sticking CVSV.

This may sound really involved, but it is very easy to diagnose this way once you know how.

There has been a service bulletin isued for that code. I have run into this before, also the wires comming out of the connector. That would bethe first thing to check. Here is what the bulletin states. Emissions - SES Lamp ON/DTC P0440 (EVAP) SetNotesFile In Section: 06 - Engine/Propulsion SystemBulletin No.: 02-06-04-044Date: August, 2002TECHNICALSubject: Service Engine Soon (SES) Light Illuminated, DTC P0440 Set (Replace Fuel Tank Evaporative Emissions Control System (EVAP) Vent Solenoid Harness) Models: 2000-2002 Chevrolet Cavalier2000-2002 Pontiac Sunfire ConditionSome customers may comment that the SES light is/was illuminated.A technician may find DTC P0440 is stored in the PCM.CauseThe EVAP solenoid harness may be misrouted around the rear antilock brake (ABS) wire harness causing a chaff/damage to the EVAP vent solenoid harness, setting DTC P0440.CorrectionFollow the service procedure below to diagnose and correct this condition.1. Install a Tech 2 scan tool and select the appropriate vehicle. Verify that a DTC P0440 is stored in the PCM. 2. Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information (SI Document ID # XXXXX).



Locate and inspect the EVAP vent solenoid harness (3) routing. The harness may be routed below the ABS wiring harness (4) at the right rear corner of the fuel tank, causing stress on the EVAP solenoid harness (3).





4.Disconnect the EVAP vent solenoid harness (3) from the EVAP vent solenoid (2) and connector C313 (1). Discard the EVAP vent solenoid harness (3).

5.Connect the new EVAP vent solenoid harness (3), P/N 22687059, to the EVAP vent solenoid (2), route the harness above the rear ABS harness (4) and connect the EVAP vent solenoid harness (3) to connector C313 (1).

6.Lower the vehicle.

7.Clear the DTC's with the Tech 2 scan tool.

If all of the wires are good you will want to check for any leaks in the evap system.

Hope helps.

scan for codes, see why light is on

Need to run a scan to see the engine code. Check engine is on is a warning from a lot of different things. What you suggested can be a coolant sensor, since it is the least expensive to replace it yourself, you could do it.
However I would buy a OBDII scan tool less than $90 to get the diagnose code then find out what is the problem, so a shop can't fool me at least. Every imported car in US after 1996 must have the OBDII port built in for diagnose scan. Your car is after 1996, it has this port to do diagnose scan. This way you will have something after doing the diagnose rather than have the shop do it for you which cost almost the same but you don't own anything at the end. Good luck.

p0440 code means that the evap system has a leak. This could be caused by a bad or improperly installed gas cap. Either that or the purge solenoid has failed or the canister is plugged and not working properly.