tannertaylormusic Posted June 30, 2010 Report Share Posted June 30, 2010 Hi guys, well finally took my 97 Deville into the mechanic and the P0300 was caused by coils. Easy enough. I asked him about the 1645 EVAP code that came up in the car, his diagnostic test did not read any problems there. I've cleared the PCM codes, drive it for a while and keep getting this darn 1645 code and the "Service Engine Light" has come back on. The car seems to be running just fine, any ideas why I'm STILL getting this code? Link to comment Share on other sites More sharing options...
Cadillac Jim Posted June 30, 2010 Report Share Posted June 30, 2010 P1645 Evaporative Emission (EVAP) Vent Solenoid Control Circuit The EVAP vent solenoid connector or wiring has a problem, or the EVAP vent solenoid is bad. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 30, 2010 Report Share Posted June 30, 2010 Circuit Description The PCM contains chips called Output Driver Modules that provide 7 switchable ground outputs for operating solenoids, relays, telltales, and other devices. Each of these ground outputs has an internal fault line that feeds back to the PCMs microprocessor. When the output is OFF, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is ON, it should receive 0 volt since it is grounding the output. If it receives 0 volt when the output is OFF or 12 volts when the output is ON, it sets the fault line low. DTC P1645 is used to monitor the fault line of the EVAP purge solenoid. Conditions for Setting the DTC Test Conditions DTC P1640 not set. Engine running at least 10 seconds. Failure Condition Fault line is low for 2 seconds. Action Taken When the DTC Sets The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails. The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records. Conditions for Clearing the MIL/DTC The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test. Use a scan tool to clear DTCs. Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. Diagnostic Aids Notice Do not apply voltage to the EVAP vacuum switch. The voltage supplied by the PCM is of a low current design. The EVAP vacuum switch may be damaged if jumpered to voltage without this current limiting feature. Use the Failure Rec. to aid in diagnosing an intermittent fault. Use the data captured when the DTC set to determine if an open or shorted condition caused the DTC to set. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
tannertaylormusic Posted July 1, 2010 Author Report Share Posted July 1, 2010 Ok, let me ask a different question.. The car is running just fine. Is this 1645 going to eventually cause problems or can I just let it go? In Minnesota, we don't have to test for Emission Standards. I know that eventually I should fix it, but is that EVAP going to leave me stranded somewhere or cause more harm to other parts? Link to comment Share on other sites More sharing options...
Cadillac Jim Posted July 1, 2010 Report Share Posted July 1, 2010 The EVAP system is the vent from the gas tank. If it never purges then pressure can build up in the gas tank. If you never park in the sun all day then this is likely tolerable, but I think that you are at risk for a gas leak if you leave the EVAP system non-functional. Conceivably, high fuel tank pressure could cause other problems like forcing off the hose to the filler tube. I wouldn't let it go if it was my car. In addition, if something else happens that turns on the MIL light you won't know unless you happen to run the codes because the MIL light is already on. The FSM write-up that BodybyFisher posed seems identical to that in my 1997 model year FSM. What it means is that either the wiring to the EVAP solenoid is bad or the solenoid itself is bad. The solenoid is easily accessible under the hood. It's an easy, inexpensive fix and not hard to troubleshoot. It's easily in DIY territory. The solenoid is under $20 at Rock Auto. Why not check the connector and make sure that it is clean and tight, and if the MIL light doesn't go off then change the solenoid? -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
tannertaylormusic Posted July 1, 2010 Author Report Share Posted July 1, 2010 That's what I needed to hear! I cleaned the connection to the solenoid last week and put a new fuse that powers that system. I will def put in a new solenoid tomorrow and let you know what I see. If it is wiring, then that's out of my ballpark - but I'll get back at you asap. Thanks guys Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 1, 2010 Report Share Posted July 1, 2010 Yes, let us know how this turns out, check all vacuum hoses for cracks and looseness Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Cadillac Jim Posted July 1, 2010 Report Share Posted July 1, 2010 You should get a tester and learn how to use it. You can check fuses for continuity and find bad fuses that have hidden or invisible cracks, see if terminals have voltage on them, check to see if a terminal is properly grounded, etc. I just checked the NAPA web site and they have either junk or professional mechanic gear ($$$). Radio Shack on the other hand has four, from $17 to $50. The list includes two temperature sensors for some reason (I searched on "multimeters"). http://www.radioshack.com/search/index.jsp?kwCatId=&kw=multimeters&origkw=multimeters&sr=1 The $17 one will work just find for testing cars. WARNING -- with any of these inexpensive meters, you can blow a fuse or burn up the meter by using it incorrectly, and reading the reviews a lot of people blow the fuse and don't know what is wrong. It costs $$$ to make a meter that is protected well from mistakes and abuse; look elsewhere and expect to pay on the order of $200 if you want that. If you want to make do for little cash but are totally uninitiated in electrical matter, read the instruction manual that comes with the meter thoroughly, then read it again the next morning. Play with it a little before you use it. If it acts up at all, there is a spare fuse inside the unit and you should take the back off and put it in; you might first want to take the whole thing to Radio Shack and get some spare fuses so you can show one to the clerk to get the right one. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Cadillac Jim Posted August 28, 2010 Report Share Posted August 28, 2010 Post moved to topic on separate P1645 problem: http://caddyinfo.ipbhost.com/index.php?showtopic=32357&view=findpost&p=173653 -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted August 28, 2010 Report Share Posted August 28, 2010 99STS's thread went here: http://caddyinfo.ipbhost.com/index.php?showtopic=30428&st=0 Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
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