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Thread: Power Distribution replaced?

  1. #1

    Default Power Distribution replaced?

    I just purchased a 2004 C5 that had been crashed and rebuilt. I'm trying to get it smogged in California. It is throwing a P0410. The check valves are good. I have read that the air solenoid could still be malfunctioning even though I am getting a good flow from the air pump when it is started up cold. I wanted to track down this, but there is no relay #40 in the Power Distribution box. There are holes for a relay, but no contacts and the diagram on the box lid indicates that #40 spot is left empty. Relay #33 is there and works fine. I am now thinking that this box was pulled out of another GM car that didn't need a relay #40. Is that possible? The rest of the box looks correct.

    Can anybody tell me if there is still a relay #40 being used in 2004? What are my options to get this P0410 cleared?

    Thanks in Advance,

    Dave
    '04 C5

  2. #2
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    Quote Originally Posted by Newbie Dave View Post
    I just purchased a 2004 C5 that had been crashed and rebuilt. I'm trying to get it smogged in California. It is throwing a P0410. The check valves are good. I have read that the air solenoid could still be malfunctioning even though I am getting a good flow from the air pump when it is started up cold. I wanted to track down this, but there is no relay #40 in the Power Distribution box. There are holes for a relay, but no contacts and the diagram on the box lid indicates that #40 spot is left empty. Relay #33 is there and works fine. I am now thinking that this box was pulled out of another GM car that didn't need a relay #40. Is that possible? The rest of the box looks correct.

    Can anybody tell me if there is still a relay #40 being used in 2004? What are my options to get this P0410 cleared?

    Thanks in Advance,




    Dave
    '04 C5


    If you are getting good air flow from the air pump that is located behind the left front bumper, then electrically you are ok. Check all the air tubes that come from the pump assembly and connect to the AIR tube assembly in front of the master cylinder, and then follow all the tubes to their respective check valves. The right side (passenger side) check valve is bolted to the back of the left cylinder head by the firewall and is hard to see, but you can follow the hose going behind the rear of the left valve cover to the check valve. With the AIR pump flowing good air as you stated, it sounds like a hose might be disconnected. Good luck with it.
    20+ years ASE and Honda Master Tech

    1998 black 6 spd convertible

  3. #3

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    Quote Originally Posted by LLC5 View Post
    If you are getting good air flow from the air pump that is located behind the left front bumper, then electrically you are ok. Check all the air tubes that come from the pump assembly and connect to the AIR tube assembly in front of the master cylinder, and then follow all the tubes to their respective check valves. The right side (passenger side) check valve is bolted to the back of the left cylinder head by the firewall and is hard to see, but you can follow the hose going behind the rear of the left valve cover to the check valve. With the AIR pump flowing good air as you stated, it sounds like a hose might be disconnected. Good luck with it.
    Thanks for the quick reply. Here is a summary of what I discovered.

    I was getting air flow through the hose at the connection near the Left fender but it wasn't enough. When I disconnected the vacuum line to the vacuum bleed valve and the flow stayed the same when I did a cold start. Plus I don't feel any vacuum at the bleed valve, but I am not getting a P0412 code, so I assume the solenoid circuit is good. I then installed an external vacuum onto the bleed valve and now I am definitely getting air flowing into the check valves where as before I detected a vacuum at the hose on the driver's side check valve. I think I am correct that if the solenoid circuit wasn't getting proper voltage reading at the PCM, the PCM would set a P0412.

    I am using a 1999 C5 manual, so I am not sure if GM changed the setup on my 2004. Maybe they eliminated the relay #40 circuit and now have the secondary air system all controlled by relay #33. Can anybody confirm that thought?

    I pulled the battery out and found a vacuum solenoid just hanging there not bolted down. They didn't bother to mount it when they put the car back together. I connected an external vacuum supply to one of the tubes and confirmed that it controls the vacuum to the vacuum bleed valve. I didn't detect any vacuum going to this solenoid, so I suspected my problem was a bad vacuum supply to this AIR solenoid. I confirmed that by connecting the external vacuum supply to the solenoid and proved everything with the AIR works when the solenoid gets vacuum.

    Next, I pulled the RF wheel and the panel off to get to the vacuum tank. It turns out they had left the vacuum tank disconnected and the tube just hanging there open. I got new vacuum lines and had everything ready to go, but I am not sure which line is for the engine vacuum so I started the car and discovered, there is no vacuum from any of the lines.

    I know one of the lines goes to the vacuum tank, one to the AIR vacuum solenoid. I suspect one goes tot he A/C controls and the other to the engine manifold. I looked through the manual and around the engine, but can't find anything. After a lot of research it appears that the vacuum port is at the rear of the manifold and will require the manifold to be removed for repairs. In the mean time, I ran a new vacuum line from the brake booster pump over and abandoned the original line that runs through wire harness. I assume there is a pretty nasty vacuum leak that I will have to pull the manifold and repair, but I hope this will get me through California smog check.
    Last edited by Newbie Dave; 09-01-2014 at 08:48 PM.

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