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Discussion Starter · #1 ·
My 2002 4.2L 2WD Trailblazer LS (not extended body) has 166K miles and a recent Service Engine Soon light for Evap Solenoid. I replaced Evap Solenoid (I don't know part vendor) in Sept 2016 at 127K miles. Then I replaced again at 144K miles in August 2020 using a Duralast part. So I am getting this error every 20K miles or so. I bought the ACDelco part just now. Before I replace again, I have a couple questions:
1) is it possible there is another Root Cause other than Evap Solenoid for the Error Code P0440? Ex: perhaps my Evap Canister is bad?
2) If I have been using second-rate parts ("Unknown" vendor on first replacement, Duralast on second replacement) can I expect better life on the ACDelco solenoid?
3) does the Evap Solenoid cycle only every time the engine is started? Or do other events (EX: driving along in hot temperatures/sun, possibly cause fuel to volatize more within the fuel tank, etc, goes into Canister)?
4) IIRC when I replaced Solenoid previously I cleared the Error Code by disconnecting Battery, then driving up to 15-20 miles cleared the SES light. But I have since read that disconnecting the battery for any reason (unless absolutely necessary...etc) is a Risk. i.e. how should I clear the SES light?
Thanks for any info...
 

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2002 Chevrolet TrailBlazer LTZ 4.2L
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What codes are you getting? Are you testing the functionality of the solenoids before replacing thing?
 

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2004 chevy trailblazer_lt
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Remember, the P0440 code is telling you there is a leak in the EVAP system. It does not say that the EVAP solenoid is defective.

Many things can cause a P0440. From P0440 Chevrolet Code - Evaporative Emission System:

|P0440 CHEVROLET code possible causes Missing or loose fuel cap Incorrect fuel filler cap used Fuel filler cap remains open or fails to close Foreign matter caught in fuel filler cap EVAP canister or fuel tank leaks EVAP system hose leaking Fuel tank leaking Faulty vent solenoid Faulty EVAP purge switch

Read more: P0440 Chevrolet Code - Evaporative Emission System

You need to diagnose the system to make sure something else is not going on.

As far as parts go, yes, there are second and third rate parts out there. There are even garbage parts. Stick to parts that come from places that have a vested interest in protecting their good name. Hence, I stick to emission parts from ACDelco, Delphi, Standard Motor Products (non T series), NAPA Echlin, or BWD (non P series). Not included are Carquest, Duralast and Dorman.

Clear the codes either by driving normally and after several drive cycles the SES light will go out as long as there is nothing else going on, or use a code reader. Heck my ~$25 dollar Bluetooth OBDII dongle and Torque Pro app combination will erase codes and clear the SES light.

Now for an important message from our combined experiences:

DO NOT DISCONNECT THE BATTERY - REMOVE THE APPROPRIATE FUSE(S). Why? Because when you reconnect the battery, the HVAC actuators inside of the dash are commanded to run a recalibration procedure which stresses the old brittle plastic gears inside the actuators and the brittle plastic gears break and leaves you unable to control where the air comes out, or control the temperature of the air, etc. Replacing at least one of them literally requires the removal of the entire dash! So, if you ever need to actually disconnect the battery, such as in the case of needing to install a new battery, be sure and use some kind of Keep Memory Alive device to avoid the HVAC actuator recalibration routine.
 

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Discussion Starter · #4 ·
Thanks to All for the inputs. I will double check but I believe the only Code was P0440 which unfortunately can mean many (at least 7) possible root Causes.

How can I test (i.e. what is the Bench Test for) functionality of my current Evap Solonoid? Remove Solonoid/Valve and apply 12V ? I haven't looked at the electrical pins yet (except for 2 years or more ago).

Given the other 6 (of possible 7) Root Causes I will continue to diagnose and will update on this forum as progress is made. I believe this VIN was in the range for Recall on Cracked Filler Hose . Dealer Records I had pulled a while back did not indicate the fix had been applied.

Thanks also for the detail on how to Clear Codes. Very helpful to avoid a possible expensive additional problem!
 

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2002 Chevrolet TrailBlazer LTZ 4.2L
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Thanks to All for the inputs. I will double check but I believe the only Code was P0440 which unfortunately can mean many (at least 7) possible root Causes.

How can I test (i.e. what is the Bench Test for) functionality of my current Evap Solonoid? Remove Solonoid/Valve and apply 12V ? I haven't looked at the electrical pins yet (except for 2 years or more ago).

Given the other 6 (of possible 7) Root Causes I will continue to diagnose and will update on this forum as progress is made. I believe this VIN was in the range for Recall on Cracked Filler Hose . Dealer Records I had pulled a while back did not indicate the fix had been applied.

Thanks also for the detail on how to Clear Codes. Very helpful to avoid a possible expensive additional problem!
The video I liked below has a really good explanation of how to change the front and rear solenoid, as well as how to bench test them for functionality.

 

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2004 chevy trailblazer_lt
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Yes, you can bench test either the EVAP Vent Solenoid or the Purge Solenoid by applying 12 VDC to the terminals and see if you can blow through the ports that connect to the hoses. If the solenoid is bad, you either won't be able to blow through it with or without 12 VDC applied, or you can blow through it with or without 12 VDC applied.
 

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2004 chevy trailblazer_lt
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Good Luck!
 

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Discussion Starter · #9 ·
OK All, I have watched a bunch of videos and am ready to dive-in hands-on. I have on-hand an ACDelco Evap Purge Valve (the one that attaches to Engine Block) and a new Gas Cap (Duralast, couldn't get locally/quickly an ACDelco) plus next week I will receive and AC Delco Evap Canister Vent Valve (located near Fuel Tank).Understanding the 7 or so possible Root Causes I inspected the Fuel Fill Assembly and it show no signs of rust so I am ruling that out, at least initially. I will next Remove/BenchTest and if necessary replace the Evap Purge Valve. A couple quick questions about Evap Purge Valve replacement: 1) I can't get good access from below so plan to reach from above--my arms seem long enough and not too "hefty" . But I would like to disconnect the Power Brake Vacuum Tank Hose which obstructs access. Is it OK to pull the rubber 90degree fitting out of the Brake Tank, or better to Undo hose clamps? Next I undo the Electrical Connecter--fairly straightforward. 2) On the "creamy white" (rearward) Hose connector is it best to push down on the Tab which is 180 degrees from the Legs? Or is there a better way to Undo this Clamp/Hose? 3) I would then lift the metal detent on the Mounting Bracket (vs. leave the 10mm bolt/bracket in-place). 4) Then Valve Assembly can be moved/swiveled for squeezing a Tab (as shown in several videos) Undo the Front Clamp/Hose. 5) to Reset the Code what Fuse should I pull? I looked at both UnderHood and RearSeat Fuse Boxes, not obvious to me which Fuse to Pull ( or may AutoZone Code Reader I borrowed has a Reset Code button. Or I break down and buy a OBDI II devise for my phone.....
Sorry about all the questions but I want to be sure I don't break anything (especially the Valve Hose Clamps). I have replaced Evap Canister Vent Valve before, but this UnderHood Valve is a bigger challenge. TIA.
 

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2002 Chevrolet TrailBlazer LTZ 4.2L
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When I did mine, I followed the linked video I shared, with a slight modification. I unhooked and disconnected all connectors and hoses first before removing them from the mount. You can unplug the 90° hose end from the brake booster without issue. It'll rebuild vacuum once reattached and the vehicle is restarted. My arms are long enough but almost hefty enough to not have been able to reach. This acted as another "hand" to hold the solenoid in place. I installed it the same way. Mounted to the bracket first and then connected everything. The clip on the one in the rear looks like the image pasted below. It will remove all the way without breaking. Put it back in first and then click the hose in place and you're done. To reset the code you need an OBDII tool. Disconnecting the battery is a cardinal sin and could lead to more backbreakinger repairs in the dash. Get the tool. A cheap 20 or 30 dollar actron will be a good basic tool to start with.
Bicycle part Font Auto part Metal Fashion accessory
 

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2004 chevy trailblazer_lt
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cprodave - in the future, more paragraphs and less "uniparagraphs" please. It will make for easier reading and digesting.

What metalmike187 said.

It sounds like you have a good plan. Also, for the code reader part, put the $25 towards this setup if you have an Android device. It will run circles around the Actron and even some of the mid- to higher level Innova code readers/live data scanners. Here goes:

Download the Torque Pro app from the Google play store - cost ~$5.00

Go to Amazon.com and get one of these:


They are currently selling for $13.99. The app and this dongle will let you monitor most anything you desire and it will erase codes and make the MIL light go off.
 

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Discussion Starter · #12 ·
MetalMike, thanks for the info on your modified technique and for the image of the rearmost clip. Of all the videos I watched (most of whom struggled with this rearmost Clip) nobody showed a good closeup view of the Clip, they mostly fumbled and forced until it cam undone.

ChemMan, sorry about not breaking up better into paragraphs. I should have known better.

I did order that Scan Tool from Amazon today for my Android so I will quit half-A**ing my diagnosis using borrowed tools!

Thanks again guys!
 

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2) On the "creamy white" (rearward) Hose connector is it best to push down on the Tab which is 180 degrees from the Legs? Or is there a better way to Undo this Clamp/Hose?
Yes, this is how they are designed to work. Pushing down on the top will cause the two legs of the clip to separate far enough to be able to slide it off the solenoid. When I reattach them I always push down on the top, but I've read that you don't really have to.
Study the picture that metalmike187 posted and you'll see how they work.
 

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2004 chevy trailblazer_lt
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cprodave, when you get the dongle and g to set up the Torque Pro app, let me know and I'll assist you in setting things up and guide you to the "hidden settings" Just DM me through the start a conversation.
 

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2004 chevy trailblazer_lt
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de nada
 
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