- Sep 2, 2012
- 468
Hi all -
Really could use a hand with this one. I've had an intermittent P0455 code for quite some time. In most cases, after a few drive cycles it would clear itself. I would say this began last fall with the onset of cooler temps, and I'd get a Code/CEL maybe once a month. I did some searching and reading back then, decided gas cap was most likely culprit, but before replacing it an inspection revealed some corrosion around the fill pipe neck that created a rough surface. I sanded and polished it smooth, clean up the rubber seal on the cap and didn't seem to get any more occurrences. In ALL cases, ONLY P0455 is set along with the CEL...no other codes stored or pending, ever.
Fast forward to about two weeks ago, just prior to my emissions test approaching. The CEL came on. I assumed P0455, and further assumed that it would again clear itself after a few cycles. It didn't.
I reset the code and cleared the CEL with my OBDlink SX, ran a couple cycles after which no MIL was illuminated, and no codes were stored or pending. I looked but failed to notice that there were two emissions monitors not ready (Evap and Catalyst) - Only 1 not ready is permitted here. As such I failed the first emissions test.
I waited the required 24 hrs, drove the required mileage and just as I was heading to get a 2nd test (still eligible for a conditional pass unless there was an increased number of not ready monitors) The CEL came back with code P0455. I cleared it, thinking I'd still just have the two not ready, and wouldn't ya know my laptop died as I was checking their status...decided to gamble and lost as I hadn't driven it enough to complete one of the diagnostics, and it failed.
So I began REALLY chasing the source. Polished the filler pipe again till shiny and smooth and bought and installed a brand new AC Delco gas cap at the dealer ($33 ugh, time pressure!) and took a 200 km trip out of town.
I got a couple drive cycles completed, back comes CEL/P0455. :-(
Since then I've read and searched like a demon. Roadie has a very nice summary of the most common causes (gas cap, vent solenoid, purge solenoid, cracked filler neck at tank). I found another post that talked of the possibility of issues under the fuse block and another that referenced a severely aged purge solenoid hose that crumbled on contact.
I tackled the vent solenoid first. Removed from vehicle, inspected, valve was open as expected, air passed easily thru. I activated the solenoid by putting 12V across the terminals numerous times, nice loud audible feedback, and semi-verified the seal by confirming no air would pass thru with solenoid closed (semi-verified because I don't have a vacuum pump).
Opened the cover at the end, inspected the foam filter for debris, cleaned out some chunks of dirt from outer edge , removed and cleaned the filter, and cleaned the interior of the canister. replaced the filter and cap, shot a squirt of wd40 in the end where you can see the spring and worked it a few more times to clear any grime that may have been on the valve seat. Before reinstalling, I verified 12V (actually got 11.46, I attribute that to the difficulty of finding a really good ground nearby) was present at the connector pink wire with ignition in Run.
This left me satisfied that my VENT solenoid is likely functional as long as the PCM commanded ground/control signal gets through. To that end I had read a post where the control signal passes thru C100 en route from the PCM to the vent solenoid, and that by grounding the relevant pin I could simulate the PCM signal and listen for the solenoid to actuate. I now believe however that was possibly a later model year reference or possibly pertained to V8 models. The wire colors and pin locations there did not cross reference to my C100. This post referenced the correct wire colors and in conjunction with a schematic I found for my 05 XL I6, I now suspect the control signal line routes directly to the fuse block with no intervening connectors.
Because I don't have a scan tool that lets me command the solenoid directly, and because another post referenced issues under the fuse block, I attempted to remove that hoping for some good access to the control signal line. I got as far as lifting it off enough for visual inspection but with the multitude of connectors underneath I felt it might be a bit of a risk to proceed. Visually there was no appearance of rust, corrosion, dirt or water intrusion that may have given rise to the issue mentioned by that poster. Not conclusive I know, but hopefully usable info.
While I was R&Ring the vent solenoid by the gas tank, I visually inspected the tank filler neck for ANY signs of past leakage....it's dry and clean and as far as I can tell from reading, the issue was mainly isolated to MY's prior to my own. The solenoid hose connectors seem secure and undamaged, and the vent hose from the tank as far as I could access it seemed intact with no kinks in the stiff plastic that might indicate a stress point where it may have cracked.
All of which left me wanting to check out the PURGE solenoid. And I TRIED...from the top, from the bottom with the wheel off, from every angle I could conceive of except for any which might have been prevented by the jack/jack stand on the front of the frame rail. The best I could manage was to get the electrical connector off, and back on when I finally gave up. I've seen videos on it, read posts on it...I still swear everyone else has a different truck!
But I left it for last because I can't envision exactly how P0455 is set by the PURGE solenoid, unless it gets stuck OPEN when the PCM initially attempts the gross vacuum leak test. But if that was the case, I'd expect other codes, poor engine behavior, SOMETHING else to go with P0455. Maybe its just slow to close in cooler weather? Remember this seems more prominent in fall and winter, worse this year than last but has gone from spring till now before setting the code...suggests to me the purge solenoid might be sluggish but not completely stuck.
Anyway, that's the background story. I know it's a pile to digest, but I figured I may as well include all the details I have now, because many of the questions responders woulkd naturally ask have been covered.
I'll end with my begging for helpful suggestions, and for the answer to two questions:
1) On 2005 XL SLT I6 vehicles, is there a convenient place as close as possible to the PCM that I can access the control line and simulate the ground signal to verify vent solenoid operation?
2) Can anyone throw up better or even any plausible ideas on exactly how the purge solenoid gives rise to ONLY P0455 with no noticeable deterioration in engine performance, no other associated codes, and only begins acting up in the fall?
Thanx,
Very much appreciate any help & suggestions...It'd be awesome if I could track this down without resorting to a trip to a shop/dealer
Really could use a hand with this one. I've had an intermittent P0455 code for quite some time. In most cases, after a few drive cycles it would clear itself. I would say this began last fall with the onset of cooler temps, and I'd get a Code/CEL maybe once a month. I did some searching and reading back then, decided gas cap was most likely culprit, but before replacing it an inspection revealed some corrosion around the fill pipe neck that created a rough surface. I sanded and polished it smooth, clean up the rubber seal on the cap and didn't seem to get any more occurrences. In ALL cases, ONLY P0455 is set along with the CEL...no other codes stored or pending, ever.
Fast forward to about two weeks ago, just prior to my emissions test approaching. The CEL came on. I assumed P0455, and further assumed that it would again clear itself after a few cycles. It didn't.
I reset the code and cleared the CEL with my OBDlink SX, ran a couple cycles after which no MIL was illuminated, and no codes were stored or pending. I looked but failed to notice that there were two emissions monitors not ready (Evap and Catalyst) - Only 1 not ready is permitted here. As such I failed the first emissions test.
I waited the required 24 hrs, drove the required mileage and just as I was heading to get a 2nd test (still eligible for a conditional pass unless there was an increased number of not ready monitors) The CEL came back with code P0455. I cleared it, thinking I'd still just have the two not ready, and wouldn't ya know my laptop died as I was checking their status...decided to gamble and lost as I hadn't driven it enough to complete one of the diagnostics, and it failed.
So I began REALLY chasing the source. Polished the filler pipe again till shiny and smooth and bought and installed a brand new AC Delco gas cap at the dealer ($33 ugh, time pressure!) and took a 200 km trip out of town.
I got a couple drive cycles completed, back comes CEL/P0455. :-(
Since then I've read and searched like a demon. Roadie has a very nice summary of the most common causes (gas cap, vent solenoid, purge solenoid, cracked filler neck at tank). I found another post that talked of the possibility of issues under the fuse block and another that referenced a severely aged purge solenoid hose that crumbled on contact.
I tackled the vent solenoid first. Removed from vehicle, inspected, valve was open as expected, air passed easily thru. I activated the solenoid by putting 12V across the terminals numerous times, nice loud audible feedback, and semi-verified the seal by confirming no air would pass thru with solenoid closed (semi-verified because I don't have a vacuum pump).
Opened the cover at the end, inspected the foam filter for debris, cleaned out some chunks of dirt from outer edge , removed and cleaned the filter, and cleaned the interior of the canister. replaced the filter and cap, shot a squirt of wd40 in the end where you can see the spring and worked it a few more times to clear any grime that may have been on the valve seat. Before reinstalling, I verified 12V (actually got 11.46, I attribute that to the difficulty of finding a really good ground nearby) was present at the connector pink wire with ignition in Run.
This left me satisfied that my VENT solenoid is likely functional as long as the PCM commanded ground/control signal gets through. To that end I had read a post where the control signal passes thru C100 en route from the PCM to the vent solenoid, and that by grounding the relevant pin I could simulate the PCM signal and listen for the solenoid to actuate. I now believe however that was possibly a later model year reference or possibly pertained to V8 models. The wire colors and pin locations there did not cross reference to my C100. This post referenced the correct wire colors and in conjunction with a schematic I found for my 05 XL I6, I now suspect the control signal line routes directly to the fuse block with no intervening connectors.
Because I don't have a scan tool that lets me command the solenoid directly, and because another post referenced issues under the fuse block, I attempted to remove that hoping for some good access to the control signal line. I got as far as lifting it off enough for visual inspection but with the multitude of connectors underneath I felt it might be a bit of a risk to proceed. Visually there was no appearance of rust, corrosion, dirt or water intrusion that may have given rise to the issue mentioned by that poster. Not conclusive I know, but hopefully usable info.
While I was R&Ring the vent solenoid by the gas tank, I visually inspected the tank filler neck for ANY signs of past leakage....it's dry and clean and as far as I can tell from reading, the issue was mainly isolated to MY's prior to my own. The solenoid hose connectors seem secure and undamaged, and the vent hose from the tank as far as I could access it seemed intact with no kinks in the stiff plastic that might indicate a stress point where it may have cracked.
All of which left me wanting to check out the PURGE solenoid. And I TRIED...from the top, from the bottom with the wheel off, from every angle I could conceive of except for any which might have been prevented by the jack/jack stand on the front of the frame rail. The best I could manage was to get the electrical connector off, and back on when I finally gave up. I've seen videos on it, read posts on it...I still swear everyone else has a different truck!
But I left it for last because I can't envision exactly how P0455 is set by the PURGE solenoid, unless it gets stuck OPEN when the PCM initially attempts the gross vacuum leak test. But if that was the case, I'd expect other codes, poor engine behavior, SOMETHING else to go with P0455. Maybe its just slow to close in cooler weather? Remember this seems more prominent in fall and winter, worse this year than last but has gone from spring till now before setting the code...suggests to me the purge solenoid might be sluggish but not completely stuck.
Anyway, that's the background story. I know it's a pile to digest, but I figured I may as well include all the details I have now, because many of the questions responders woulkd naturally ask have been covered.
I'll end with my begging for helpful suggestions, and for the answer to two questions:
1) On 2005 XL SLT I6 vehicles, is there a convenient place as close as possible to the PCM that I can access the control line and simulate the ground signal to verify vent solenoid operation?
2) Can anyone throw up better or even any plausible ideas on exactly how the purge solenoid gives rise to ONLY P0455 with no noticeable deterioration in engine performance, no other associated codes, and only begins acting up in the fall?
Thanx,
Very much appreciate any help & suggestions...It'd be awesome if I could track this down without resorting to a trip to a shop/dealer
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