P0411 Troubleshooting

Discussion in 'V8 - Maintenance & Troubleshooting' started by gamefanatic, Nov 2, 2020.

  1. gamefanatic

    gamefanatic SHO Member

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    So I have had the error, like I'm sure many have had, for more than 2 years. Well, it's time to get a smog check again, but this code keeps coming back up and as one would guess fails the secondary air check. This is the only code I get.

    What I have done so far:
    1. Validated vacuum lines are good using hand vacuum (a few times).
    2. Validated the Air Injection bypass solenoid is working both out of the car and in the car. Turns on and enables the vacuum to route to the AIRD.
    3. Validated vacuum to the AIRD is more than 10 psi. (Can't remember the exact value.)
    4. Validated the AIRD is working. With the car off, applied 5-15 psi to the vacuum port of the AIRD, on the Air Pump inlet I applied ~15 psi air. With vacuum applied no backpressure.
    5. Validated the Air Pump is working. It was working, but I replaced it with a junk yard pull off a '99 a year ago. Every time the car starts up the pump turns on and I can feel suction.
    6. Validated operation of motor by using Mode-6 command to turn it on.
    7. Setup my Torque app to monitor the AIRM. At least when I'm sitting still (which is about the only time it comes on) I hear the pump turn on and off with my monitor.
    I'm at a loss what to do next outside of bypassing it with a tune. :bonk:
     
  2. SHOZ123

    SHOZ123 SHO Member

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    Did you take the lines off that run from the diverter valve to the manifolds to make sure they are clean and open? Same with the diverter valve.
     
  3. 99sho-time

    99sho-time SHO Member

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    was the cat ypipe changed?
     
  4. gamefanatic

    gamefanatic SHO Member

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    I wasn't able to actually remove the nut to the hot / exhaust side. But the hose going to the diverter is clean. I may have to try harder, but I know the one I got recently out of the junk yard, I had to cut out.

    For what it is worth the junk yard version I cut out showed no signs of build up at all on the hot side. I validated the pressures against this so I could run shop air through the system and get a good idea of how things would flow.
     
    Last edited: Nov 2, 2020
  5. gamefanatic

    gamefanatic SHO Member

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    Nothing done to the CAT's. No apparent holes or rattling coming from there or around the O2's. Still in stock form and parts.
     
  6. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    My two cents (or ideas)

    I have the same code now going on and off but I still hear the pump working.

    I think the pump rather than stop working, could lose some power and air flow wat some point. It could be odd after all this time but how much mileage the '99 in scrapyard had ? (Hope not 300k.)

    The other thing is something that Paul help me with recently but I remised the car just after and I cannot say if it can related but it could. I had trouble with all the IAC valves I put on mine (original, used cleaned, new, etc). I had random misfires and near stall sometimes. On mine, throttle body was a little bit too much closed and IAC valve was working on his extreme opening (or kind of). Engine seems to suffer a lack of oxygen in some situations. Openning up a little bit the TB (adjusting the stopper screw) helped me with the misfires and the near stalls.

    Long story short, your mesure is taken at the cat but the oxygen coming from 2 places at the moment of the measurement (not in the SAI hoses).

    Thanks you Paul by the way for all the infos you directly or indirectly gave to me. I own you some beers (a pack ?) :)
     
    Last edited: Nov 13, 2020
    SHOZ123 likes this.
  7. gamefanatic

    gamefanatic SHO Member

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    Well I am looking into this some more this weekend. Right now I am looking to get at the AIRD and validate there is no abnormal blockage. I was excited to see from the JY part that there are two star security screws that are mounting an intermediate pipe connection. I should be able to get at those pretty easily to get it pulled out. I doubt I could find a tool to get in at the exhaust nut.

    I do have my other SHO I can swap parts from that is able to pass this check. This would eliminate the possibility of a second weak pump.

    If this doesn't work, I need to dig further into the computer logic like you are mentioning. As would be expected, nothing in the pinpoint tests would point to other components causing problems.

    It's worth looking into the intake side of things.
     

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