Ross Posted March 4, 2009 Report Share Posted March 4, 2009 I've searched this and I'm still trying to remedy this issue. I've gotten this code several times - the first time it came on and I looked it up, I went back and opened/re-closed the gascap just to make sure I had put it on good....nothing after about 40 miles or so. So I cleared the code. Didn't come on until about a week later with the same thing - instead of clearing it I left it alone and it went away on its own. Now I'm completely confused. I also have noticed a drop in fuel economy from about 14 or so around town to about 11.5 The SS is my daily driver so its the same commute everyday. If the problem is a bad gascap seal - how do you test it? If the problem is the purge valve - how do you test it? And if this is the issue how do you change it? I'm trying to isolate the issue so I can fix the vacuum leak issue. Thanks in advance!! -Ross Quote Link to comment Share on other sites More sharing options...
detjoe Posted March 5, 2009 Report Share Posted March 5, 2009 check the brake booster hose, my clamp was not on all the way giving me issues. Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted March 5, 2009 Report Share Posted March 5, 2009 According to AllData..... DTC P0455 SYSTEM DESCRIPTION The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge solenoid valve open and the EVAP canister vent solenoid valve closed. This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge solenoid valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, this DTC sets. DTC DESCRIPTOR This diagnostic procedure supports the following DTC: DTC P0455 Evaporative Emission (EVAP) System Large Leak Detected CONDITIONS FOR RUNNING THE DTC Before the powertrain control module (PCM) can report DTC P0455 failed, DTC P0496 must run and pass. DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0156, P0157, P0158, P0160, P0161, P0220, P0442, P0443, P0449, P0451, P0452, P0453, P0454, P0464, P0496, P0502, P0503, P1111, P1112, P1114, P1115, P1121, P1122, P1125, P2135 are not set. The engine is running. The ignition voltage is between 10-18 volts . The barometric pressure (BARO) is more than 75 kPa . The fuel level is between 15-85 percent . The engine coolant temperature (ECT) is between 4-65°C (39-149°F) . The intake air temperature (IAT) is between 4-75°C (39-167°F) . The start-up ECT and IAT are within 9°C (16°F) of each other. DTC P0455 runs once per cold start. CONDITIONS FOR SETTING THE DTC The EVAP system is not able to achieve or maintain vacuum during the diagnostic test. ACTION TAKEN WHEN THE DTC SETS The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. CONDITIONS FOR CLEARING THE MIL/DTC The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. A current DTC, Last Test Failed, clears when the diagnostic runs and passes. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. Clear the MIL and the DTC with a scan tool. DIAGNOSTIC AIDS To help locate intermittent leaks, use the J 41413-200 Evaporative Emission System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. Introducing smoke in 15-second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner. A temporary blockage in the EVAP canister purge solenoid valve, purge pipe, or EVAP canister could cause an intermittent condition. Inspect and repair any restriction in the EVAP system. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT. Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition. Quote Link to comment Share on other sites More sharing options...
benjaminh2 Posted March 5, 2009 Report Share Posted March 5, 2009 replace the evap vent solenoid. its sticking open, not allowing the purge solenoid to pull a vacum on the system. i've done a ton of em. Quote Link to comment Share on other sites More sharing options...
IndySilveradoSS Posted March 5, 2009 Report Share Posted March 5, 2009 yeah i had the same code also, i had a hole in the top of my purge canister, so not wanting to spend the 35 at the stealership, i rtv'd the hole closed and reset the comp. no probs yet. I also noticed a drop in fuel mileage, but nothing that drastic. good luck Quote Link to comment Share on other sites More sharing options...
Ross Posted March 6, 2009 Author Report Share Posted March 6, 2009 (edited) replace the evap vent solenoid. its sticking open, not allowing the purge solenoid to pull a vacum on the system. i've done a ton of em. Thats what I was expecting to hear. Any chance you have a part #? I'd rather order it from gmpartsdirect. Thanks everyone for the help. Edited March 6, 2009 by Ross (see edit history) Quote Link to comment Share on other sites More sharing options...
Ross Posted March 27, 2009 Author Report Share Posted March 27, 2009 OK this is really irritating me. Since this I have replaced the gascap just for the hell of it...code came back on. Cleared code... Code comes back on after a week or so. Cleared code... I just walked outside and replaced the purge solenoid valve located on top of the intake manifold.... Start is up...code is on again. Any ideas? According to GM if it was the canister itself it would be throwing the p0449 or p0446 I think it was. Thanks again Quote Link to comment Share on other sites More sharing options...
budhayes3 Posted March 28, 2009 Report Share Posted March 28, 2009 I believe that the mentioned EVAP vent solenoid is located back by the canister, it is different from the purge solenoid...be sure to check all of the vacuum hoses in the EVAP system, as well as inspecting the charcoal canister for cracks... Quote Link to comment Share on other sites More sharing options...
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