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Thread: Mazda 6 diesel issue? - Beginning to annoy me now.

  1. #1
    Regular Member Ste's Avatar
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    Vehicle : Jaguar XF 3.0D V6

    Trim : Black

    Engine : 3.0D V6

    Year : 0000

    Default Mazda 6 diesel issue? - Beginning to annoy me now.

    The engine warning lamp keeps coming on, and a fault code reader gives


    # P0401 - Exhaust Gas Recirculation (EGR) Flow Insufficient
    # P0404 - Exhaust Gas Recirculation (EGR) Open Position Performance

    The car doesn't behave any differently with it on. I have reset the lamp serveral times, and twiddled with the EGR valve (removed, cleaned, checked for vacuum leak etc) and it comes back on a few days later.

    The main question is this, what part isn't functioning correctly? I wonder if the vavle is partially seized, as it is very stiff to move the diaphram plate upwards through the side holes in the valve body. Is this normal? Also, if the vacuum pipe is disconnected from the actuator side, should you be able to move the valve position by sucking on a piece of tube attached to the vacuum port (like you can on other cars).


    Bit stuck now, and would really appreciate some help....

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    ********Complete speculation warning**********

    Perhaps you need to look at it from another angle? How does the ecu know if it isn't performing properly? Does it get some sort of feedback from the device (doubt it) or does it measure something else (O2 perhaps) to see if it's working properly. Perhaps the lambda or something else is at fault?

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    Regular Member Ste's Avatar
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    Vehicle : Jaguar XF 3.0D V6

    Trim : Black

    Engine : 3.0D V6

    Year : 0000

    Default

    There is an electrical valve position measuring device on the top of the vacuum side housing, with a plunger to measure deflection.

    I have been thinking of a scheme to detect whether it is the valve or the control of it that is at fault.

    I don't think it has a lambda sensor on it.

  4. #4
    Regular Member Ste's Avatar
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    Vehicle : Jaguar XF 3.0D V6

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    Engine : 3.0D V6

    Year : 0000

    Default

    Well, for completeness and maybe any help to anyone else.

    The EGR valve is operated by vacuum from the vacuum pump. In the line from the vac pump are 2 air solenoids. One opens the line from the pump to the EGR valve actuator side, the other 'T' s into this line and exits in the air filter box. This second solenoid activates to draw air into the evacuated lines to close the EGR valve (as there is no longer a vacuum). I did some tests with a vacuum guage and determined that the second air solenoid valve was not operating and was continually passing air through and hence resulting in non operation of EGR valve, and fault codes P0401 and P0404.

    So, today I removed the offending valve and dismantled it. The metal mounting was extremely rusty, and the insides were very stiff to move. After a rub down with fine sand paper and a squirt of WD40, applying +12V across the electrical terminals resulted in a positive click on and click off (whereas before I stripped it down, nothing happened when 12V was applied)

    So, job done and cost me nothing (apart from about 1/2 hour of my time)

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    Great bit of detective work however - did it clear the codes?!

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    Regular Member Tadpole's Avatar
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    Well done Ste always satisfying to get a result that only costs time ........

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    Regular Member Ste's Avatar
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    Vehicle : Jaguar XF 3.0D V6

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    Year : 0000

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    As regards to clearing to FCs. I don't know yet. As I disconnected the battery and that turned the light off.

    Will have to wait a little while before it runs the diagnostic to see if it's actually worked. I really can't see why it wouldn't work though, as the part was clearly defective and this would have caused the FC that were present.

    It usually took a couple of days for the light to come back on after I have previously cleared the light. I've had a quick look before but not as indepth as now.

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