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p0412 and p0418 Codes Wont Stay Away

This is a discussion on p0412 and p0418 Codes Wont Stay Away within the General Help forums, part of the LSx Technical Help Section category; I replaced Air Pump but I've yet to hear it go on. How much air should it push? I feel ...

  1. #1
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    p0412 and p0418 Codes Wont Stay Away

    I replaced Air Pump but I've yet to hear it go on. How much air should it push? I feel some air but it's very light and it feels like it's coming from the exaust rather than the pump.

    Replace Air Pump Solenoid with brand new one.

    Tested and validated that relays and fuses are all good but I always get these two codes just minutes after a cold start. If I clear the codes after it's warmed up they never come back so I think it's the cycle where the computer sends extra air into the exhaust to use more gas and air to heat up the catalytic converters faster when it's cold.

    I'm not sure the air pump is turning on, is there a way to test it outside the car. There are 3 leads, black red and pink. I'm thinking I can just apply 12 volts to red and black and hopefully this will turn it on, but I'm not sure what the pink is for. I have a great multimeter and am familiar with general electronics.

    I can remove and reinstall the whose system with my eyes closed, I've done it so many times so any help anyone can provide would be greatly appreciated.

    The codes started showing up when I drove through a large puddle during a rain storm.

    I'll send over some pictures tomorrow of the components. I haven't replaced the air check valves but I'm not seeing any water in the pump so I think they're working.

    My current theory is that I've got a bad pump from checkers, but I'm not sure how much air should be blowing when it's on.

    Anything else I should try?
    Last edited by rmecham; 04-22-2011 at 10:59 PM.

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    Moderator Cutlass's Avatar
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    It'll blow alot of air, like a hair blower on high. Power up the red wire and ground the black. The pump should run. The pink wire is for an internal air flow valve. It may also need to be powered up to open it and allow air flow. I can't remember for sure though. It might be normally open without power.
    I guess try it both ways and see what happens.

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    Thank you for the info. I'll give it a shot and report the results.

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    Senior Member bigrondownhiller's Avatar
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    Did you also check that you have power going to the pump?

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    Thought I had it, evil code p0412 and p0418 still showing up

    I tested the air pump I got from O'riely's using a 12 volt power source and didn't get any response so I took it back and paid for another, more expensive one, from Autozone.

    The autozone one came yesterday so I tested it with 12 volts off the battery and got the pump to work so I thought, "Ha, ha that was it."

    I connected the new autozone pump electrically, cleared the codes and ran at idle for about 5 minutes and didn't get the code to come back, even after revving the engine a few times. So I then hooked up the blower intake and output tubes and mounted the pump and then restarted the car and drove it around until it was nice and warm and still didn't get the code to come back, so I thought I had this thing by the nads, so I congradulated myself and went to bed.

    I got up this morning, started the car and within 3 minutes of drive the check engine light came on again with the p0412 and p0418 codes.

    I've checked relays, fuses, validated that the pump works when hard wired and replaced the solenoids. The only thing I haven't replaced is the valves that keep water from the exhaust from going back into the pump. Is it possible that this could throw a code?

    Thanks for all your help and to anyone that can help shed some light on this predicament.

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    Moderator Cutlass's Avatar
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    P0412 can only set if the "AIR Solenoid" relay is bad...or the PCM is bad...or the wiring/connection in between. Thats the only thing tested by this code.

    P0418 is the same way. It can only set if the "AIR pump" relay is bad...or the PCM is bad...or the wiring/connection in between.

    So technically their isn't any way it could the pump or the check valves causing these codes

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    Veteran 0rion's Avatar
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    Quote Originally Posted by Cutlass View Post
    P0412 can only set if the "AIR Solenoid" relay is bad...or the PCM is bad...or the wiring/connection in between. Thats the only thing tested by this code.

    P0418 is the same way. It can only set if the "AIR pump" relay is bad...or the PCM is bad...or the wiring/connection in between.

    So technically their isn't any way it could the pump or the check valves causing these codes
    that's what I was thinking......I was also kinda wondering about the wiring between the pump and relay because he said he ran through some water prior to this happening. Maybe got some water in the wires causing a short? Could just be coincidence though. That wiring should be fairly easy to test for a short so that's probably what I would do first since it's easy and free.

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    Solenoid

    Thank you for the information. I'll check for continuity from the relay port to where it hooks up to the pump. I checked the fuse and tested the relay but you're right there could be somehting fubar in the wiring.

    As far as the Air Solenoid, I believe I replaced it, just to validate, it's the only other electrical component mounted down on the air pump housing, it's small relative to the pump, about a quarter of the size of an average humans hand, correct?

    They Solenoid, has a rubber connector that expands to two hook ups, one that's attached to the small tube and one thats a filter/manual valve looking thing that just sits out in the open air. The small hose seems to be connected to the one of the larger air pump hoses though a connector of some sort on that hose, but I 'm not sure if it's the air intake or output hose, it makes sense to me that it's on the the air pump output hose. And then there's an electrical hookup, which I'd imagine goes to the computer. Is this right?

    I don't really understand how the solenoid works, my understanding that that it basically controls the amount of air that is allowed to be sent into the exhaust, is that accurate?

    If so, I theoroize that it does it do this by sending signals to the computer change the speed/pressure of the air pump based on the solenoid's settings and I'm assumping that this solenoid works off of air pressure pushing it rather than a vaccum pulling it. Depending on how much air is pushing the solenoid where triggers different signals telling the computer to "tune" the air pump? Is this why it needs a smaller tube so it can drive the solenoid off of the large amount of air that comes from the pump? Maybe I reversed the two hose connector that connects to the solenod?

    Am I even close . Maybe I got a bad solenoid from Checkers, it seemed to happen with the air pump, and it goes with my luck :.

    I'm going to pull it all out again tonight and just run though every compoent again, this time including a check of the wiring.

    Thanks again for everything guys. I'm sure glad there are people out there nice enough to help out.

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    I guess the small hose code be hooked to air intake side

    I guess the small hose could be hooked to air intake side, this would make more sense from the perspective that I have the impression that solenoids typically work from a vacume level.

    I'll double check when I get home and take some pictures of the objects I'm trying to describe.

    Thanks again guys.
    Last edited by rmecham; 04-28-2011 at 11:13 AM.

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    Moderator Cutlass's Avatar
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    The AIR solenoid Relay powers up 2 things at the same time. It powers the AIR Bleed Valve (the valve next to the AIR pump) and the integral stop valve (built into the pump, the Pink wire).
    Here's what the Service manual says about this stuff:
    The system includes the following:
    •AIR pump - The AIR pump is mounted to the lower left front of the engine Compartment and supplies the air to the AIR system. The electric air pump pressurizes fresh air and pumps it to the check valves near the exhaust manifolds. The AIR pump is controlled by the PCM. Battery voltage to the AIR pump is controlled by the AIR pump relay. An integral stop valve prevents air flow through the pump during OFF periods. When the PCM provides a ground circuit for the secondary AIR pump relay, battery voltage is allowed to power up the AIR pump.

    •Vacuum Bleed Valve - This valve helps prevent vacuum buildup within the AIR system, which could prevent the integral stop valve from opening. The bleed valve is controlled by the air solenoid relay and is energized when the AIR pump is commanded ON. If the vacuum relief system is not functioning, the vacuum will cause the AIR pump integral stop valve not to open. This may result in no air flow to the exhaust manifolds or delay the delivery of air which may not allow the diagnostic to pass.

    • Check valves - The check valves prevent back flow of exhaust gases into the AIR pump in the event of an exhaust backfire.

    •Necessary plumbing.
    -Hoses
    -Pipes
    -Clamps

  11. #11
    Moderator Cutlass's Avatar
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    And remember, these codes are for the control side only of the Relays. Not the load side(pump and solenoids).
    The wiring you want to check is the between the PCM and the Relays. NOT the relays and the pump/solenoids.

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