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Lambda Sensors

edited 30 November -1 at 1:00AM in Motoring
6 replies 525 views
driverlesdriverles Forumite
7 Posts
edited 30 November -1 at 1:00AM in Motoring
Hi there can anyone help me i have a 1.6 Ford Fusion that has 2 Lambda Sensors fitted are they usually the same part number and type of sensor i was asked earlier by a parts company if they were regulating or diagnostic sensors, there is 1 on top of the cat and 1 at the bottom of the cat
Thanks in advance Les


  • colinocolino Forumite
    5.1K Posts
    Part of the Furniture 1,000 Posts Combo Breaker
    Unlikely they'll be the same part number as they do slightly different jobs. Easiest thing to do is look if it is pre or post cat (One nearest the engine or the one downstream). Don't buy a cheapy or a universal one as you will have to just repeat the job in days/weeks/months when it goes out of range.
  • thanks for that i take it that 1 is regulating sensor and the other is diagnostic sensor but which is which
  • MankysteveMankysteve Forumite
    4.3K Posts
    Part of the Furniture Combo Breaker
    You'll need to replace which ever one y either way as even a diagnosis plug will throw up eml light. Presumably the second is the diagnosis one to make sure the cat is working.

  • forgotmynameforgotmyname Forumite
    31.5K Posts
    Part of the Furniture 10,000 Posts Name Dropper
    Diagnostic one? Never heard them called that before.

    The 1st one measures the exhaust gas, The 2nd one does the same but after the CAT. They are different.

    With a decent diagnostic tool you can see the outputs from each one.

    The 1st one is fairly erratic as it controls the fuelling to get the best emissions. The 2nd one is a bit slower to react as the gas at that point should be fairly stable.

    I watched a video on them and they guy was brilliant. But its 2 hours long.
    Censorship Reigns Supreme in Troll City...

  • colinocolino Forumite
    5.1K Posts
    Part of the Furniture 1,000 Posts Combo Breaker
    Both will set the eml but the pre-cat is the one doing the donkey work signalling the ecu, trying to get the air/fuel ratio to be at 14.7/1 (apart from on light or full throttle) and I suppose you could term that the regulator. The post-cat one is fine tunng the emissions and, squinting with one eye, you might call that a diagnostic.
  • londonTigerlondonTiger
    4.9K Posts
    unlikely to be the same part. the pre costs more than post. Because they have different functions. so cant be the same as everyone would just buy the post.
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