Need help to solve a P1645 code
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Need help to solve a P1645 code in Past Cadillac Vehicle Discussion; I did a search about this problem and it looked like it would one of two problems. It could be ...
  1. #1
    the4quads is offline Cadillac Owners Member
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    Need help to solve a P1645 code

    I did a search about this problem and it looked like it would one of two problems. It could be either a defective Evap. purge solenoid or a break in the wiring. One of the members found the wire broken internally just behind the connector by the valve. The wire felt good so I ordered a OEM valve from Rockauto and installed it. I cleared the code and a second or two later the "service engine soon" light popped on.
    I probed the Pink wire and it had battery voltage so maybe the Dk.Green/white wire is damaged somewhere. According to the FSM, that wire goes to #24 terminal on the PCM. I removed the multi-wire connector from the PCM and did a continuity test (three times) while wiggling the wire and I had no interruption of continuity.
    I believe that the 1645 code is a electric problem not a vacuum leak. Any ideas?

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    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    What's the code definition?

    Are you using the diagnostic tree in the FSM?

  4. #3
    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    The code definition is "EVAP PURGE SOLENOID OUTPUT CIRCUIT". I think that is the solenoid on the valve cover. If its the one down by the fuel tank, I will trouble shoot that circuit. The fuse for it is good. I checked both fuses in front for the ECM and the one under the seat. I did not check the wiring out back.

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    I was looking around and searching the forum and it looks like the "Vent" valve is on the right side of the valve cover near the EGR. I replaced the "Purge"valve on the left side of the valve cover. I'm going to check the vacuum lines and electric wires tomorrow to the "Vent" solenoid just in case. .

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    Quote Originally Posted by the4quads View Post
    The code definition is "EVAP PURGE SOLENOID OUTPUT CIRCUIT". I think that is the solenoid on the valve cover. If its the one down by the fuel tank, I will trouble shoot that circuit. The fuse for it is good. I checked both fuses in front for the ECM and the one under the seat. I did not check the wiring out back.

    ----------

    I was looking around and searching the forum and it looks like the "Vent" valve is on the right side of the valve cover near the EGR. I replaced the "Purge"valve on the left side of the valve cover. I'm going to check the vacuum lines and electric wires tomorrow to the "Vent" solenoid just in case. .
    Correct

  6. #5
    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    Well I found the "VENT" solenoid. Some said it was near the EGR valve but on my year/model its above the drivers side rear control arm. It's not to bad to get to. I should get a P1646 code if it has any electrical problems but the P1645 still indicates the "PURGE" solenoid. I'm not sure what the next step is trying to solve the P1645 code. The wiring,solenoid, and connectors are all good. Hopefully someone here solved the same problem.

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    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    Almost forgot, HAPPY EASTER!

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    Ranger's Avatar
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    Re: Need help to solve a P1645 code

    Oops! Right you are. The vent solenoid (#9) is under the car. The purge solenoid (#4) is on the cam cover near the EGR valve.

    http://www.gmpartsgiant.com/Page_Pro...007&SortKey=52

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    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    I ordered the "VENT" solenoid and will put it in this weekend. I don't usually just change parts but the two solenoids were cheap enough and will be eliminated them from the equation. Time will tell.

  10. #9
    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    Well I ran out of ideas. I replaced both the PURGE and VENT solenoids with OEM parts. I checked the wiring for broken leads, corrosion, continuity, and proper voltages. There are no apparent leaks in the lines but I think if there were leaks, I would get different codes. The only current code is 1645. When I clear it, I comes back on in 1-2 seconds.
    Anybody have some ideas? I am open to any suggestions.

  11. #10
    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    Quote Originally Posted by the4quads View Post
    Well I ran out of ideas. I replaced both the PURGE and VENT solenoids with OEM parts. I checked the wiring for broken leads, corrosion, continuity, and proper voltages. There are no apparent leaks in the lines but I think if there were leaks, I would get different codes. The only current code is 1645. When I clear it, I comes back on in 1-2 seconds.
    Anybody have some ideas? I am open to any suggestions.
    I've read on some other forums that the Output driver module (ODM) inside the PCM might be bad. That device is what grounds various circuits including the EVAP solenoids. I would need a Tech II to trigger the PURGE solenoid and check for a ground signal at the solenoid terminal.

  12. #11
    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    A friend of mine is also a mechanic and has access to Alldata. I explained to him everything I did so far and he ran down the possible causes. It seems that I covered all the common possibilities. There where two Techs. that ended up changing the PCM to solve the problem.
    In case I have to change the PCM, is there a vender or member here that could program the replacement PCM for my car?

  13. #12
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    Re: Need help to solve a P1645 code

    After you figure shipping and all, you might just be cheaper (not to mention quicker) having a dealer do it.

  14. #13
    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    I will check it out with the dealer. I have one last test to do before I throw the towel in.

  15. #14
    98Geldog is offline Cadillac Owners Fanatic
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    Try replacing the connector. A bad contact could trigger codes

  16. #15
    the4quads is offline Cadillac Owners Member
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    Re: Need help to solve a P1645 code

    One of my first tests involved opening up the lock part of the PURGE solenoid connector and pulling/tugging on the wires to check if the wire was broken inside the insulation. After that I back probed with my fluke to check for continuity. The terminals are like new- clean and shiny.
    My last test will be in two parts. One is to remove the connector at the PURGE solenoid and jump the two terminals together. I'll check for continuity between the load side of the fuse (fuse removed) thru to the #24 terminal by the PCM. The PCM wire connectors will be both disconnected. Second will be to put the fuse back in, connect the PURGE solenoid connector, ignition on and check for battery voltage at the #24 terminal by the PCM. If both check out, I'll presume the PCM has a bad component in it.
    If I buy a PCM with matching numbers, would that work or at least let me drive the car to the dealer for final reprogramming?

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