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PAIR system-DTC 442 & DTC 172 900 1997

posted by  larry139 on  Tue Jul 27 08:36 CST 2004
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I have installed new charcoal cannister, new air mass sensor, new fuel pump (by volvo dealer), and spent almost $2500 to get check engine light off. Car has about 175,000 and runs good with reasonably good gas mileage (22-25 mpg), although less than when new. Volvo dealer has been unable to correct problems.
How do you find out if air pump is working? Can you go directly from battery to pump to check? How cna I check to see if air pump solenoid is OK?
I have despaired of Volvo and have not been able to find local Volvo independent who has confidence in ability to solve problem. Help!
--
L R Hicks








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    posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

    Why did you spend all that money without a definative diagnoses?

    The DTC-442, which corresponds to an OBD-II P0410, is a flow fault in the Pulsed secondary air system. When mine did that, the cause was a rotted $1.00 rubber connector between the plastic tube and the valve.

    The major parts of the sytem are (1) the solenoid on the driver's side, which controls vacuum to the (2) valve located on the right side of the engine mid way and about even with the valve cover. (Connected by the plastic tube running over the top of the engine.) This valve isolates the (3) pump from the exhaust system when the pump isn't running. There is a larger, about 1" dia., hose between the pump and the valve. The pump is controlled by the ECU via a (4) relay. (Don't try to run the pump with the hose connected and the valve closed, or either the pump will stall, or the hose will blow.)

    The only '172 code in my book is the OBD-II one for long term fuel trim, P0172. When my car did that, I needed a new manifold gasket to cure a leak which made the engine miss when idling.

    Tell us more so we can help you.
    --
    '96 965 with 16' wheels at 117K. Had '85 745 Turbo Diesel for 200K.



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      posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

      jbowers: first question, I have been dumb, naive, and foolish...OK? Local dealer and three different shops, have been unable to give me specific cures..repairs were "best guess", I suppose. Oh well, poorer but hopefully wiser.

      Thanks heaps for your reponse. Have determined following since last posting:
      1. purge valve ok. valve is normally closed unless engine running.
      2. Plastic hose over engine to air pump solenoid valve ok.
      3. Have determined with my Volvo Parts, Inc. buddy that "Pierburg" valve below purge valve is the EGR vacuum control valve.
      4. It appears that this EGR valve is the culprit. It has a small black knob on side opposite the vacuum inlet hose that turns several turns rather easily. Assume this to be some sort of control of vacuum between inlet and the vacuum line to the air pump solenoid valve. When I bypassed this valve with engine running the air pump came on immediately. Still have check engine light on, but I can get reset, I suppose.

      I suspect this has been the problem with the check engine light all along. So much for Volvo customer service...Where would one be without Brickboard responders. Many thanks for your help & hope someone else can benefit from my
      problem.
      --
      L R Hicks



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        posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

        OK, but....

        The cannister purge sustem is completely seperate from the Pulsed Secondary Air System.

        The big valve by the side of the engine is for isolating the air pump when it is off. I believe there is no "EGR" valve in the system now that the car has a dual catalytic converter, dual O2 sensors, OBD-II ECU etc.

        My Volvo shop manual refers to the valve that controls vacuum to the AIR valve simply as a solenoid even though it controls vacuum.

        Just trying to clarify things, hope this helps. I'll refresh my knowledge tonight by reviewing the manual.
        --
        '96 965 with 16' wheels at 118K. Had '85 745 Turbo Diesel for 200K.



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          posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

          jbowers:

          Thanks for input.

          The "EGR"(?) valve in question has a 2-conductor connector to what appears to be a ceramic covered device, perhaps a solenoid. However, by-passing the device with the inlet vacuum hose to the outlet vacuum hose turns the air pump on, whether the 2-c connector is connected or not. I assume valve works from an external signal opening the valve to permit the vacuum to extend to the air pump solenoid valve.
          Speculating further, I suppose the air pump pumps fresh air into the manifold to "lean" the exhaust mixture whenever the exhaust gas is otherwise too "rich", as determined by either the exhaust O2 sensor or the cat O2 sensor. If The sensor says the mixture is too "rich", I suspect the ECU sends its signal via the 2-C connection to the valve solenoid which opens the valve, permitting the vacuum to go to the air pump solenoid valve and turns the pump on. Perhaps this also somehow signals the pump to turn on simultaneously with the vacuum valve opening. Does this make sense? I have already confessed to being a "brickhead, brickboard dummy", so any ideas or comments are gratefully accepted!
          --
          L R Hicks



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