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Thread: M and S lights again

  1. #1
    Join Date
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    M and S lights again

    Hey guys, the disco has been running great for a whole week, but my M and S lights have returned. I get the same two CAN system codes I was receiving before, but the problem is fixed by swapping out the smaller relays (maybe relay 5-8 in the engine fuse box)

    I don't know anything about relays or wiring, but it feels like new relays is a bandaid onto the bigger problem, whatever is causing the relays to fail. Where would you guys start searching to try and find the problem? I will get the error codes when I can rescan the truck, but until I swapped the relays the codes couldn't be cleared and the truck was stuck in limp mode

  2. #2
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    Just an FYI, not so much help to resolve your issue.

    I sometimes get M&S on my D2, and randomly ..

    Last time I actually remembered what and why it happened.
    I pulled up in my driveway and turned engine off, but then switched ign(only) back on to lift windows up(I had door opened).
    May have been maybe 5 sec with key off and back on. At that point battery was charged due to a min half hour drive... so not a low battery issue there.

    At that time couldn't be bothered to check it with nanocom(why M&S on), and I thought check it tomorrow.

    Then it's tomorrow ... and M&S lights gone.
    Arthur.

    All these discos are giving me a heart attack!

    '99 D1 300Tdi Auto ( now sold :( )
    '03 D2 Td5 Auto
    '03 D2a Td5 Auto

  3. #3
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    Not long after I bought Mine, it was doing the same thing. I had bought it from a dealer so I took it back to be fixed. they told me they had to re-solder a wire that had come loose somewhere on top of the transmission. whatever it was, it fixed the problem.

  4. #4
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    Adarewyr,

    Most likely the contacts for the relays are starting to age and cause poor connections, simply removing and reseating will briefly fix the issue but not cure it.

    AK83,

    You most likely had a CAN timeout fault, code P1843. This will be because the 2 controllers have lost communication because of the quick ignition cycling getting comms out of sync, I'm not sure if the controllers continue to try and communicate with each other after this, but once the code is thrown you get M & S and it goes into limp mode until restarted.

    Turning the ignition off for several seconds and then restarting will fix it, but the fault will still be logged.

    Sharmy,

    The autobox wiring loom runs over the top of the auto and actually lays on the top of the box. Over a couple hundred thousand km of vibration, the shielding wears through and will cut one or more wires.

  5. #5
    Join Date
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    Quote Originally Posted by shack View Post
    Sharmy,

    The autobox wiring loom runs over the top of the auto and actually lays on the top of the box. Over a couple hundred thousand km of vibration, the shielding wears through and will cut one or more wires.
    Rubs through on the P clip. PITA but simple fix. PITA because you'll need to pull out the console etc to fix it properly. Also, the AC drain dropping right into the XYZ switch was a stroke of genius.
    ​JayTee

    Nullus Anxietus

    Cancer is gender blind.

    2000 D2 TD5 Auto: Tins
    1994 D1 300TDi Manual: Dave
    1980 SIII Petrol Tray: Doris
    OKApotamus #74
    Nanocom, D2 TD5 only.

  6. #6
    Join Date
    Aug 2025
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    Quote Originally Posted by shack View Post
    Adarewyr,


    AK83,

    You most likely had a CAN timeout fault, code P1843. This will be because the 2 controllers have lost communication because of the quick ignition cycling getting comms out of sync, I'm not sure if the controllers continue to try and communicate with each other after this, but once the code is thrown you get M & S and it goes into limp mode until restarted.

    Turning the ignition off for several seconds and then restarting will fix it, but the fault will still be logged.
    Thanks, this is very helpful as I've had something like this a couple of times this year on my '99 D2, and had the feeling it was something to do with the key slipping when turning on, or being too fast... I had the fault code you mentioned, and was able to clear it without difficulty (so far!).

    Cheers, Myles
    '99 D2 Td5 Auto (native)
    2004 D2a Td5 Auto (tuned)
    ('97 D1 V8, off herding sheep somewhere)

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