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code po 400 850

posted by  NAILS on  Sat Jun 26 13:49 CST 2004
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I have a po 400 code malfunction in my 96 850. Exhaust gas recirc. malfunction. How should I procede in addressing this? What may be causing this?








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    code po 400 850

    posted by  Hamfisted on  Sun Jun 27 14:34 CST 2004
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    With the engine running see if the vacuum hose to the EGR is getting a vacuum. If not check for cracks in the hose. Do you have a code reader that can reset the ECU? Try resetting it and see if it repeats.

    Mike


    Here's some more troubleshooting tips from the shop manual:

    Code P0400 (EGR System, Flow Malfunction)

    1) Turn ignition on. Use Volvo Scan Tool (998-8686) parameter
    Diagnostic Test Mode No. 3 and check EGR controller functions. If EGR
    controller operates, go to next step. If EGR controller does not
    operate, go to step 7).

    2) Turn ignition off. Disconnect wire at EGR controller
    connector terminal No. 2. Connect a jumper wire between EGR controller
    connector terminal No. 2 and ground. Start engine and run at idle. If
    engine runs unevenly at idle, fault is intermittent. Go to step 11).
    If engine does not run unevenly at idle, go to next step.

    3) Turn ignition off. Carefully remove White hose from EGR
    controller. Connect vacuum gauge to White hose. Start and run engine
    at idle. If vacuum gauge gives any reading, go to next step. If vacuum
    gauge does not give a reading, ensure White vacuum hose and connection
    to intake manifold are not blocked.

    4) Start and run engine at idle. Connect White hose to EGR
    controller. Carefully disconnect Yellow hose from EGR controller.
    Connect a vacuum gauge to EGR controller connector. Connect loose wire
    on EGR controller to ground so as to open EGR controller. If vacuum
    gauge gives any reading, go to next step. If vacuum gauge does not
    give a reading, retest using new EGR controller.

    5) Turn ignition off. Carefully disconnect Yellow hose from
    EGR valve. Check Yellow hose for leaks or obstruction. Repair as
    necessary. If hose is okay, go to next step.

    6) Turn ignition off. Connect Yellow hose to EGR valve.
    Connect vacuum pump to Yellow hose at EGR controller. Start engine and
    run at idle. Pump vacuum to maximum of 4.35 psi (30 kPa). Check that
    EGR valve retains vacuum. Engine should run unevenly when vacuum pump
    shows negative pressure. If engine runs evenly when vacuum pump shows
    negative pressure but vacuum pump loses vacuum, test using new EGR
    valve. If engine runs smoothly at idle when vacuum pump shows negative
    pressure and vacuum pump retains vacuum, check if EGR pipe is clogged.
    Repair as necessary. If EGR pipe is okay, retest using new EGR valve.

    7) If EGR controller does not operate, turn ignition off.
    Disconnect EGR controller connector. Turn ignition on. Connect
    voltmeter between EGR controller connector terminal No. 1 and ground.
    If battery voltage is present, go to next step. If battery voltage is
    not present, check wiring between EGR controller connector terminal
    No. 1 and main relay connector terminal No. 3 for an open circuit.

    8) Turn ignition off. Disconnect EGR controller connector.
    Disconnect ECM connector. Connect breakout box to ECM connector.
    Reconnect ECM. Connect ohmmeter between breakout box pin No. 40 and
    EGR controller connector terminal No. 2. If ohmmeter reads zero ohms,
    go to next step. If ohmmeter does not read zero ohms, check wiring
    between EGR controller connection terminal No. 2 and breakout box pin
    No. 40 for an open circuit.

    9) Turn ignition on. Disconnect EGR connector. Connect
    voltmeter between breakout box pins No. 40 and 42. If voltmeter reads
    less than one volt, go to next step. If voltmeter does not read less
    than one volt, check wiring between EGR controller connector terminal
    No. 2 and breakout box pin No. 40 for a short circuit to voltage.

    10) Turn ignition off. Ensure EGR connector is connected.
    Turn ignition on. Use Volvo Scan Tool (998-8686) to check if EGR
    controller functions. If EGR controller functions, code was caused by
    poor contact in control module and/or EGR controller connector. Repair
    as necessary. If EGR controller does not function, retest using new
    EGR controller.

    11) If fault is intermittent, check EGR controller connection
    and ECM connectors for signs of loose connection and contact
    resistance. Check wiring between EGR controller connector terminal No.
    2 and ECM connector terminal No. 40 for an intermittent open circuit.
    Also check wiring between EGR controller connector terminal No. 1 and
    main relay connector terminal No. 3 for an intermittent open circuit.







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