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ECM re-install V70-XC70

posted by  Robert S. on  Tue Jun 15 16:52 CST 2021
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last visit: Sun Sep 21 05:48 CST 2014
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2000 V70 SE, Denso, AW-5, 278K miles

Been chasing this gremlin for a long time: Misfire on cylinder #3. It occurs randomly, CEL lights up, and after fixing you can count on it occurring again, with no predictable interval between episodes. It can be after 10 miles, 100 miles, 1,000 miles, but the misfire and CEL will always re-appear and it's always cyl 3.

All my troubleshooting and fixes have worked, but only temporarily. Have swapped coils, installed a new #3 coil, changed plugs, repinned a new #3 coil receptacle housing (twice), spliced (crimp + solder) four new wires from the #3 coil as far upstream into the harness as I can get, and checked/cleaned all grounds. The car will run great after the troubleshooting and fix, until the misfire / CEL occurs again. Always #3. The local Indy shops are stumped - no help from them.

Because the engine runs so well when all cylinders are firing, I have ruled out a cylinder compression issue but had it tested anyway at the Indy shop. All five cylinders test at over 160.

Some will suggest that an entire set of new coils might solve the problem (why I'm not sure, if there's only one problem cylinder). Some will suggest the ECM has a problem with triggering #3 coil, or high resistance in a coil wire somewhere along the routing from ECM to coil.

Regarding the ECM, can it be unplugged, terminals cleaned and then replugged? Ocean salt air corrosion takes a toll on electrical connectors here, and so the V70 would not be immune from corroded connectors.

Q: Can Xemodex or other vendors test check the ECM, before saying it needs to be rebuilt?

Any ideas appreciated,
Robert








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    ECM re-install V70-XC70

    posted by  KlausC on  Wed Jun 16 11:34 CST 2021
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    last visit: Fri Oct 24 10:15 CST 2014
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    Use electric contact cleaner and a soft toothbrush to clean the ECM contacts. A microfiber cloth works well also.

    There is always the possibility that #3 injector has dirt. A couple bottles of good injector cleaner added to 1/2 tank of gas may help, rather than pulling the injectors and having them professionally cleaned.
    --
    Keeping it running is better than buying new








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    ECM re-install V70-XC70

    posted by  derek uk on  Wed Jun 16 05:03 CST 2021
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    last visit: Fri Oct 24 12:33 CST 2014
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    Do you get the ETS light (this is the ECM)? If you don't get that it probably isn't the problem. CEL light common fault, I read, is a bad fuel cap. giving random signals due to a bad seal. You've not mentioned a bad injector as a possibility for your misfire problem. See if you can run a Vida scan when the CEL light is on. CEL light reset is easy on this model, no tool needed.
    My 2000 V70XT (P1/P80) had ETS problems and I converted it to full electronic with a Sacar module. Not expensive, £75 on UK eBay, and not difficult to do if you are handy and follow the instructions to the letter. See RobertDIY on YouTube. Unless you are that man in which case I'm not probably going to be helping you much!!! I also had a bad vacuum leak from one of the small tubes that goes to the front right of the intake manifold. That helped with my tick over as the computer was trying to correct for a weak mixture and making it too rich.








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      ECM re-install V70-XC70

      posted by  Robert S. on  Thu Jun 17 08:43 CST 2021
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      last visit: Sun Sep 21 05:48 CST 2014
      [RELATED]

      Have ruled out injector problem, since it's a #3 coil ignition issue. CEL appears only when there is a #3 misfire and engine starts running rough, suggesting it is not a gas cap sealing problem.

      A typical troubleshooting scenario on this car:
      - I'll pull dead cyl #3 coil while engine is running.
      - Coil is dead (not arcing against spark plug well).
      - Sometimes when the #3 coil is moved around a bit in spark plug well, it will start arcing again.
      - The usual temporary fix: swap coils, engine smooths out as #3 is firing again, button it up, and the car runs fine until #3 is dead again at random intervals. Coils (spare coil too) are relatively new from Bosch
      - New NGK standard plugs installed 2K miles ago. I don't the think spark plugs are the problem.

      Will a bad injector kill the ignition coil for that cylinder; i.e., are they tied together?








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    ECM re-install V70-XC70

    posted by  Chris Mullet on  Tue Jun 15 21:52 CST 2021
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    last visit: Fri Oct 24 09:08 CST 2014
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    This is the tool to unlatch and relatch the ECM and TCM:

    https://www.ebay.com/itm/202143908386?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=202143908386&targetid=4581183927179145&device=m&mktype=&googleloc=&poi=&campaignid=418233787&mkgroupid=1241348861725295&rlsatarget=pla-4581183927179145&abcId=9300542&merchantid=51291&msclkid=7ba692d5f1df1f03f55af21c83fe4d11

    Some people say they can do the task with a skinny screwdriver. I tried that method and failed.

    Oxidation of those contacts is probably not uncommon. I know of one case where the owner foolishly purchased a new Bosch throttle body due to repeated error messages related to throttle movement when all it ended up needing was the ECM contacts cleaned.

    Incidentally I have a spare throttle body sitting on the shelf…..







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