Write-up: EVAP Filter Canister Replacement for 97 Riviera (SES/DTC P0441)

Thought I would share my recent experience troubleshooting DTC P0441 on my ’97 Riv that ultimately led to EVAP Canister replacement (also replaced EVAP Purge Solenoid Valve and Vacuum Switch). For you “pros” this is probably very elementary, but I had never worked on the EVAP System before so it was all new to me. Previous posts on this topic were very helpful, but didn’t provide details on EVAP Canister Replacement.



Also, I do not own an OBD Tech 2 Scanner (just a simple Code Reader) so I had to go with a “part-swapping” approach instead of detailed scanner troubleshooting. I spent about $150 on parts from RockAuto. In hindsight, I could have purchased less but I chose to perform the more simple procedures first and, at the same time, replace old parts that were probably on their way out anyway.

So here it goes…hope this may help someone else with these same symptoms:
• SES (Service Engine Soon) light ON
• DTC (Diagnostic Trouble Code) P0441 on Code Reader
• No noticeable operating problems (such as running rough, gas odors, etc.)

Procedures:
1. Locate the EVAP Purge Solenoid Valve and Vacuum Switch toward the rear of engine bay.



2. Inspect the hoses/lines in-and-around these two devices for visible cracks, breaks, etc.

NOTE: During this step for my Riv, I observed a broken Purge Line (the line going all the way back to the EVAP Canister near the gas tank), as well as the line going between the Purge Valve and Throttle Body. Fixed them both with new hoses/line. On the Purge Line (and in between the Purge Valve and Vacuum Switch), you can see I simply used a piece of vacuum line hose (only filtered vapors go through this line; not actual fuel). For the Throttle Body, ordered a new line for about $20 (GM part no 24506665 for the Bonneville; see this post for details: https://rivperformance.editboard.com/t10889-evap-solenoid-to-throttle-body-vacuum-line?highlight=EVAP+Throttle).

3. Make note of the EVAP Purge Solenoid Valve (1) and Vacuum Switch (2) hose connection scheme, and then carefully remove the hoses/lines from both these devices.



4. Remove these two devices from their mounting brackets by pressing the bracket release tabs and lifting them up-and-out from the brackets

5. Once removed, gently tap the Purge Valve and/or Vacuum Switch hose connector-ends on a clean sheet of white paper and note whether or not black charcoal debris comes out. If it does, you likely have a bad EVAP Canister because normally charcoal should never leave the canister and go up through the Purge Line. If no debris, one or both of these devices may be defective and probably should be replaced.



NOTE: Charcoal within these devices indicates that the EVAP Canister is defective and leaking charcoal pieces up through the Purge Line to the Purge Valve/Vacuum Switch.  As shown in the photo, I had charcoal debris but chose to replace both of these devices anyway at a total cost of around $40+ (RockAuto). (I also replaced the fuel gas cap just to be sure.)

6. Locate the EVAP Canister on the inside of the driver’s side rear fender. Note the actual EVAP Canister is housed in a round, black plastic protective case which also provides its mounting bracket.





7. On the EVAP Canister hoses, mark the purge line (closest to the muffler) with a piece of duct tape and another piece of tape on the canister case, aligned in the same location for future reconnection identification.



8. Loosen and remove the canister mounting bracket bolt (only one) with a 10mm socket ratchet. Once the bolt is removed, support the canister the best you can with one hand so that you do not place excessive strain on the attached hoses. They are probably old and brittle!



9. Carefully remove the hoses from the old canister by pulling them off the outlet connectors. Note the illustration and photo show how the hoses connect and the direction that you should pull.

NOTE: I was able to remove the hoses with finger-power only.





10. With the hoses removed, bring down the canister case so that it is oriented top-to-bottom, and the mounting brackets clear the muffler and fender rubber edge-rib.

CAUTION: Since my canister was defective, charcoal powder started coming out when rotated; be careful to wear eye/nose protection while doing the removal.

11. Completely remove the canister by rocking it left-to-right while pulling it straight down. You may have to gently push away the muffler (it sways on its mounting hanger) to provide adequate clearance.

NOTE: The Riv Service Manual recommends removing the muffler hanging bracket, but I found this unnecessary.

12. From the engine bay, clean out the Purge Line by blowing compressed air into the line from the engine-side (Purge Line disconnected from Vacuum Switch and EVAP Canister, of course).

13. Re-attach the Purge Line to the Vacuum Switch.

14. Before removing the old canister from its protective case, note and mark the orientation of the case top cover to its lower case for future re-assembly.

15. Remove the old canister from its protective case by releasing its three (3) top cover tabs, lifting the cover off and pulling the canister up and out.

16. If necessary, clean out any charcoal debris from inside the canister case.

17. Insert the new canister into the case in the same orientation as the old and securely snap on the top cover.

18. Reinstall the canister case into its mounting area of the rear fender in the opposite way that it was removed.

19. Attach the vacuum hoses to their proper connector locations, pressing-in firmly to make sure they are securely connected.

20. Slide far end of the canister case’s mounting bracket into the provided slot.

21. When properly positioned, insert and tighten the 10mm mounting bracket bolt.

DRIVE CYCLE ROUTINE
The following procedures explain how to reset the DTC code, and prep your Riv’s PCM (Powertrain Control Module) for Emission’s Inspection by performing appropriate drive cycle routines.

Using a DTC Code Reader/Scanner tool of choice (I use an inexpensive Model U480 CAN OBD2 LCD Engine Scanner Fault DTC Code Reader), erase the fault codes.



NOTE: Perform the following GM Drive-Cycle Routines to allow the PCM to activate (Ready) all necessary monitoring circuitry so that your Riv’s Emission’s System will be ready for inspection. This process should take 15 to 30 minutes if done consecutively.

1. From a Cold Start, run the engine for two-and-a-half minutes with the air conditioner ON and rear defroster ON. (The more electrical load you can apply the better.) This will test the O2 heater, Passive Air, Purge "No Flow," Misfire and if closed loop is achieved, Fuel Trim.

NOTE: To be classified as a cold start, the engine coolant temperature must be below 122 degrees F (50 degrees C) and within 11 degrees F (6 degrees C) of the ambient air temperature at startup. Do not leave the key ON prior to the cold start or the heated oxygen sensor diagnostic may not run.

2. Accelerate - Turn OFF the air conditioner and all the other loads and apply half throttle until 55mph (88km/hr) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

3. Hold Steady Speed - Hold a steady speed of 55mph (88km/hr) for three (3) minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.

4. Decelerate - Let off the accelerator pedal. Do not shift, tap the brake, etc. Be sure to allow the vehicle to coast along, gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

5. Accelerate - Accelerate at 3/4 throttle until reaching 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 2.

6. Hold Steady Speed - Hold a steady speed of 55mph (88km/hr) for five minutes. During this time, in addition to the diagnostics performed in step 3, the catalyst monitor diagnostics will be performed. If the catalyst is marginal, or if the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.

7. Decelerate - This will perform the same diagnostics as in step 4. Again, don't press the brakes or shift gears.

8. Code Reader – Once again view the code status, making sure there are not DTC codes and that the appropriate I/M systems are “ready” before going for your emissions inspection.

Hopefully all is well now with your SES light remaining OFF and no more troublesome EVAP System DTC codes!  

Good info. I also noticed charcoal bits in my EVAP system along with the same code. I have since just disabled the EVAP until I decide to spend the money to replace the canister on a system which does not seem to effect much of anything. However I would like to be "check engine" free.

Where is the EVAP canister on a 98 Riviera. I don't see one there on my car. I'm getting a P0442 code. If I turn the SES light off with my scan tool. It takes several weeks for it to come back on. Seems the car is failing the EVAP readiness test, and that doesn't happen under certain conditions (cold temps and a full tank to name a few). Tried looking in my FSM, but haven't found much to help.

LARRY70GS wrote:

Where is the EVAP canister on a 98 Riviera.  I don't see one there on my car.  I'm getting a P0442 code.  If I turn the SES light off with my scan tool.  It takes several weeks for it to come back on.  Seems the car is failing the EVAP readiness test, and that doesn't happen under certain conditions (cold temps and a full tank to name a few).  Tried looking in my FSM, but haven't found much to help.

You should see it by the fuel filter under the car.  It looks different than the above pictures, but you'll see lines running into it and it is attached to the car with three bolts.  It's a foot long rectangle box.

Thanks, I'll get under there and have a look. When I fill the tank, I get a fuel smell from outside the car after driving home from the station. It's on the left side for sure. Keeps lighting the SES light with code P0442, small leak in EVAP system. It passes all the readiness tests one at a time until the EVAP test. That test will only run when the fuel tank is a certain full range. If I keep the tank full or close to it, it won't run the test. In NY, a 98 can pass inspection with 2 readiness tests not completed, so no big deal. Hoping it is simply a cracked rotted hose or something simple.

LARRY70GS wrote:

Thanks, I'll get under there and have a look.  When I fill the tank, I get a fuel smell from outside the car after driving home from the station.  It's on the left side for sure.  Keeps lighting the SES light with code P0442, small leak in EVAP system.  It passes all the readiness tests one at a time until the EVAP test.  That test will only run when the fuel tank is a certain full range.  If I keep the tank full or close to it, it won't run the test.  In NY, a 98 can pass inspection with 2 readiness tests not completed, so no big deal.  Hoping it is simply a cracked rotted hose or something simple.

When this happened on my car it was a corrosion hole in the filler pipe. Found using a smoke machine.

Did you/can you smoke the system? If not here is a DIY smoke machine. If nothing else, take a look to have a grin... basically, it's a sealed paint can attached to a shop air supply thru a propane regulator, burning incense sticks stuck in floral arrangement foam, and it works quite well. See the link: https://www.youtube.com/watch?v=2U5kFib1WxE

"real" smoke machines are mad pricey: https://www.amazon.com/OTC-LeakTamer-Smoke-Diagnostic-Machine/dp/B007X74ZTK

I am not saying teh DIY smoker is a good idea - I have to find ot if the smoke generated thus harms the evap system. HOWEVER if not, what a win... Heck, this is worth digging into. Can the fittings be obtained (the rubber cone gadget) and can one make one's own incense sticks with that UV dye stuff? Or install a device to create smoke using the "factory approved" smoke fluid?

Just love a challenge - this is like the DIY power brake bleeder... gives a new meaning to "blow smoke up their ***..."

Albertj

LARRY70GS wrote:

Where is the EVAP canister on a 98 Riviera.  I don't see one there on my car.  I'm getting a P0442 code.  If I turn the SES light off with my scan tool.  It takes several weeks for it to come back on.  Seems the car is failing the EVAP readiness test, and that doesn't happen under certain conditions (cold temps and a full tank to name a few).  Tried looking in my FSM, but haven't found much to help.

The rear bumper hides it somewhat. Its directly above the left side muffler.

th3fr4nchi5e wrote:

LARRY70GS wrote:

Where is the EVAP canister on a 98 Riviera.  I don't see one there on my car.  I'm getting a P0442 code.  If I turn the SES light off with my scan tool.  It takes several weeks for it to come back on.  Seems the car is failing the EVAP readiness test, and that doesn't happen under certain conditions (cold temps and a full tank to name a few).  Tried looking in my FSM, but haven't found much to help.

The rear bumper hides it somewhat. Its directly above the left side muffler.

Not on the 98. It is further forward. I'll get under there when it stops raining and warms up.

albertj wrote:

LARRY70GS wrote:

Thanks, I'll get under there and have a look.  When I fill the tank, I get a fuel smell from outside the car after driving home from the station.  It's on the left side for sure.  Keeps lighting the SES light with code P0442, small leak in EVAP system.  It passes all the readiness tests one at a time until the EVAP test.  That test will only run when the fuel tank is a certain full range.  If I keep the tank full or close to it, it won't run the test.  In NY, a 98 can pass inspection with 2 readiness tests not completed, so no big deal.  Hoping it is simply a cracked rotted hose or something simple.

When this happened on my car it was a corrosion hole in the filler pipe. Found using a smoke machine.

Did you/can you smoke the system? If not here is a DIY smoke machine. If nothing else, take a look to have a grin... basically, it's a sealed paint can attached to a shop air supply thru a propane regulator, burning incense sticks stuck in floral arrangement foam, and it works quite well. See the link: https://www.youtube.com/watch?v=2U5kFib1WxE

"real" smoke machines are mad pricey: https://www.amazon.com/OTC-LeakTamer-Smoke-Diagnostic-Machine/dp/B007X74ZTK

I am not saying teh DIY smoker is a good idea - I have to find ot if the smoke generated thus harms the evap system. HOWEVER if not, what a win... Heck, this is worth digging into. Can the fittings be obtained (the rubber cone gadget) and can one make one's own incense sticks with that UV dye stuff? Or install a device to create smoke using the "factory approved" smoke fluid?

Just love a challenge - this is like the DIY power brake bleeder... gives a new meaning to "blow smoke up their ***..."

Albertj

Thanks Albert. Not sure if my club director has a smoke machine in his shop. Going to my Spring car club meet on Sunday, but driving the 1970 GS 455 Stage1. I'll ask him.

Yes, my first thought was the fill pipe. The sheet metal is rotted there, but the fill pipe looks good. I can clearly see it between the body and tire when putting gas in the car. If it was leaking, I'd be able to see it as well as smell it when putting in gas. I can't. I also thought maybe the fuel pump mounting might be rotted and creating a leak there. I unbolted the inspection panel and looked, it looks good. Don't see any fuel ,leaking anywhere. Hoping it is one of the hoses to the canister. The leak has to be pretty small, the code description says so.

https://www.obd-codes.com/p0442

@Larry: it could even be a wornout gas cap. I am on my 4th.

Albertj

albertj wrote:

@Larry: it could even be a wornout gas cap. I am on my 4th.



Albertj

That's interesting, I have never changed mine. What happened to the other 3? How did you know they were bad? What replacement did you use? Stant? http://www.rockauto.com/en/moreinfo.php?pk=48606&cc=1303322&jsn=422

LARRY70GS wrote:

albertj wrote:

@Larry: it could even be a wornout gas cap.  I am on my 4th.



Albertj

That's interesting, I have never changed mine.  What happened to the other  3?  How did you know they were bad?  What replacement did you use?  Stant?  http://www.rockauto.com/en/moreinfo.php?pk=48606&cc=1303322&jsn=422

For various reasons part of the standard tool crib at a GM dealer is a gas cap tester. I knew the caps were bad because they'd fail the tester.

The GM caps have improved over the years; it's been quite a while since I've had to replace mine.

Stant is one of the OEMs, I think; Blau is the other. The Stants have a big "S" on them as you can see in the RockAuto pictures, and the Blau have this more or less unintelligible scribble. It's a Blau T48 or T28 - GM, thank goodness, uses a lot of hard parts like gas caps across large numbers of car lines for many years running.

I maybe should not say this but I was told there was an issue with the elastomer used to seal the cap in certain aftermarket caps. If you take off the cap - the elastomer seal is the rubbery circular gasket that seals when you screw down the cap onto the filler neck. One reason the OE caps cost so much is the gasket they use. Some of the gaskets used on the aftermarket GM caps would get hard and then not seal properly, which the PCM would code as a small evap leak. My observation (over 17 years of owning & driving this Riviera) was the Blaus and the OE Stants (bought at dealer) last longer than the aftermarket Stants to the point where I won't bother with the aftermarket caps unless I lose a cap/cap fails while traveling or some such.

By the way, if the cap is not bad, rust or dirt at the mouth of the filler neck where is is supposed to seal up is enough to cause a leak big enough to set a code.
For that, though, you can just stick a rag in the opening (so you don't get grit in the tank) and sand the mouth of the neck smooth. Even an emery board will work for that job. Other than that check if your gasket is hardened or dirty. If dirty try cleaning it with dry gas. Hardened means you can't really dent it with your fingernail. Good way to figure this one out is go to the auto parts store, take in your gas cap, and poke the gasket of any new cap for a GM car -- then compare yours. The gasket will discolor long before it gets hard; hardening is a problem.

albertj

Thanks again Albert. Plan is to get under there and make sure that the canister is intact and check the hoses. If that looks good, I'll try replacing the cap.

LARRY70GS wrote:

Thanks again Albert.  Plan is to get under there and make sure that the canister is intact and check the hoses.  If that looks good, I'll try replacing the cap.

If it's any consolation the parts guy at a nearby dealer will test my cap n/c if I suspect it's bad. Sometimes it is, sometimes not. All the tester is, essentially, is a mityvac-looking gadget with a gauge.

Got under there today. The canister has some surface rust around it, but looks otherwise undamaged. Both hoses look good and are pliable. Took my original gas cap off, and the seal is dried out and worn. Will try a new cap.

LARRY70GS wrote:

Got under there today.  The canister has some surface rust around it, but looks otherwise undamaged.  Both hoses look good and are pliable.  Took my original gas cap off, and the seal is dried out and worn.  Will try a new cap.

bingo... (probably)

We will see. I'll get the PCM to do the EVAP test once I replace the cap. I'll keep the tank close to full until then. My NYS inspection isn't due till end of June, so I have time. I ordered the AC Delco cap with the tether off EBay.

LARRY70GS wrote:

albertj wrote:

LARRY70GS wrote:

Thanks, I'll get under there and have a look.  When I fill the tank, I get a fuel smell from outside the car after driving home from the station.  It's on the left side for sure.  Keeps lighting the SES light with code P0442, small leak in EVAP system.  It passes all the readiness tests one at a time until the EVAP test.  That test will only run when the fuel tank is a certain full range.  If I keep the tank full or close to it, it won't run the test.  In NY, a 98 can pass inspection with 2 readiness tests not completed, so no big deal.  Hoping it is simply a cracked rotted hose or something simple.

When this happened on my car it was a corrosion hole in the filler pipe.  Found using a smoke machine.

Did you/can you smoke the system?  If not here is a DIY smoke machine.  If nothing else, take a look to have a grin... basically, it's a sealed paint can attached  to a shop air supply thru a propane regulator, burning incense sticks stuck in floral arrangement foam, and it works quite well. See the link: https://www.youtube.com/watch?v=2U5kFib1WxE

"real" smoke machines are mad pricey: https://www.amazon.com/OTC-LeakTamer-Smoke-Diagnostic-Machine/dp/B007X74ZTK

I am not saying teh DIY smoker is a good idea - I have to find ot if the smoke generated thus harms the evap system.  HOWEVER if not, what a win... Heck, this is worth digging into.  Can the fittings be obtained (the rubber cone gadget) and can one make one's own incense sticks with that UV dye stuff?  Or install a device to create smoke using the "factory approved" smoke fluid?

Just love a challenge - this is like the DIY power brake bleeder... gives a new meaning to "blow smoke up their ***..."  

Albertj

Thanks Albert.  Not sure if my club director has a smoke machine in his shop.  Going to my Spring car club meet on Sunday, but driving the 1970 GS 455 Stage1.  I'll ask him.

Yes, my first thought was the fill pipe.  The sheet metal is rotted there, but the fill pipe looks good.  I can clearly see it between the body and tire when putting gas in the car.  If it was leaking, I'd be able to see it as well as smell it when putting in gas.  I can't.  I also thought maybe the fuel pump mounting might be rotted and creating a leak there.  I unbolted the inspection panel and looked, it looks good.  Don't see any fuel ,leaking anywhere.  Hoping it is one of the hoses to the canister.  The leak has to be pretty small, the code description says so.

https://www.obd-codes.com/p0442

Further on the fuel pipe - if the leak (rust perforation) is somewhere up near the mouth of the pipe, just behind where it passes thru the fender, it will not likely leak gas.

Fill pipe looks good along it's entire length. I don't see any problem with it as of yet.I may have been smelling gas from the cap not sealing. I only notice it just after I have filled the tank and drive home.

LARRY70GS wrote:

Fill pipe looks good along it's entire length.  I don't see any problem with it as of yet.I may have been smelling gas from the cap not sealing.  I only notice it just after I have filled the tank and drive home.

Lucky you, right behind the fender was where mine developed a pinhole. Fender was (and still is) clean as a new whistle.

Would not surprise me at all that you'd smell gas from a cap not sealing right. BTDT.

Pretty shot don't you think? LOL. New one will be here Monday.

So I filled up the tank yesterday. This morning after taking a drive, I smelled an odor of fuel from the passenger side rear. Took a look and there was a fuel stain on the right side of the fuel tank. It may in fact be leaking from the fuel pump to tank seal up top when the tank is full. I will have to remove the inspection cover before I fill the tank next time. Last time I looked the pump looked good. The retainers were rusted a bit, but the pump was not popped up any. That must be my problem. If fuel is leaking out, air can get in.

+1 on the leak. As for the cap, you have to poke the gasket with your finger - it should be firm and not brittle. Clean the rust off the end of the fill pipe opening and clean the cap gasket with some solvent that wont attack the plastic.

96_Juggernaut wrote:

Good info. I also noticed charcoal bits in my EVAP system along with the same code. I have since just disabled the EVAP until I decide to spend the money to replace the canister on a system which does not seem to effect much of anything. However I would like to be "check engine" free.

"Good info"? Juggernaut is a harsh critic - this is awesome info! My '97 SC has been throwing that code since long before I owned it and for the first time since I've owned it I need to pass an emissions test and soon. Very well done and great photos and diagrams! Thank you for taking the time!

Well, I finally figured out what my problem was. I took another look at my fuel pump by removing the inspection panel. The locking rings and tabs were toast. I left the panel off and opened the trunk while filling the tank. Just as the gas pump clicked off, I saw fuel spill around the pump mounting. When I went to remove the locking ring, the whole thing just disintegrated.



I had a new Delphi pump, and my original had gone nearly 172,000 miles on my original so



Lucky for me, I had one of Ken Lisk's replacement for the gas tank tabs. I attached it to the gas tank with 5 stainless screws and nuts.



Then the new pump and locking ring.



My problems were not over yet. It still leaked when I filled the tank. I found while the ring and new tabs worked to secure the pump, it did not push the pump down sufficiently to seal. My remedy was to shim the locking ring down. Seems to be tighter now, but I am waiting now to see what happens when the PCM runs the EVAP test. All my other readiness tests have run and passed. It seems there has to be certain conditions for the EVAP test to run. The tank needs to be at less than 3/4, so I haven't tried to fill it up yet. We will see what happens.