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93 gm tbi flashing 42 and 72 code

Discussion in 'The Garage' started by bad_bo_ti, Feb 6, 2005.

  1. bad_bo_ti

    bad_bo_ti 1/2 ton status

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    as title says, what the heck do i need to look for, 42 i think is a spark or timeing code and 72 is something to do with speed sensor i think. just looking for help. thanks, chris
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Find what the codes mean online...plenty of results from searching Google I would think. It's OBD-1 codes, will be the same for all OBD-1, or at least to the best of my knowledge.
     
  3. bad_bo_ti

    bad_bo_ti 1/2 ton status

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    42 is spark monitor and 72 is output speed loss.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Ugh...sorry, neither one of those means a THING to me.

    Spark monitor probably means something along the lines of coil/module/etc. problems, output speed loss might mean the ECM is watching the engine RPM and comparing to vehicle speed, and its not matching what the ECM thinks the relationship should be.

    However, I have never heard of those two descriptions for codes, so that is pure speculation. You are sure those are OBD-1 codes, not OBD-2?
     
  5. 1979jimmy350

    1979jimmy350 1/2 ton status

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    i looked in my factory manual and those are the right descrption for the codes because he has a 4l60 E with it throwing a code 72 the tranny goes into a mode with maxium line pressure no TCC and soft landing second gear only it is casused by two successive speed readings have more then 1000 RPM(Difference must be more than 1500 RPM in P and N) This is word for word from the GM service manual on the 4l60-E
     
    Last edited: Feb 7, 2005
  6. dirtwarrior17

    dirtwarrior17 Banned

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    I don't know anything about this subject but wouldn't that mean bigger tires would make your motor run worse? seems like the ecm should be able to compensate.....
     
  7. dirtwarrior17

    dirtwarrior17 Banned

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    the tranny goes into a mode with maxium line pressure to TCC and soft landing second gear only it is casused by two successive speed readings have more then 1000

    Is there an english section in that manual?
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    ECM has to be told there is a difference. It has no idea the gears or tire sizes have changed, only that the output shaft RPM is XX, and XX RPM to the ECM means XX MPH. The ECM doesn't "see" vehicle speed from the wheel, that data is gathered before the differential. (again, tranny/t-case output) So anything changed after the tranny/t-case, the ECM can't "see" and has to be "told".
     
  9. eagle mark

    eagle mark 1/2 ton status

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    42. Fault at electronic spark timing circuit (sets when timing is set also, clear code and verify that it does not return.)

    Have you set your timing with the wire disconected? If not it may be EST in the distributor.

    Pull the batterey cable for a minute or so and reconnect. This will clear the codes and try again.
     
  10. dirtwarrior17

    dirtwarrior17 Banned

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    that makes sense but what about the mechanical speedo?
     
  11. 1979jimmy350

    1979jimmy350 1/2 ton status

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    what do you mean mechanical speedo a 93 would have a electronic speedo
     
  12. Thunder

    Thunder 3/4 ton status

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    Code 42. Electronic spark control Circut problems. Either your magnetic pick up coil or possibly the dist module. Probabally the magnetic pick up coil. Its the round thing around the dist shaft. Have to pull the dist to change it out.

    Code 72. No Vehicle speed signal. Check the VSS sender on the Xfer case it may have been un plugged. or is malfunctioning. The computer is seeing no siginal from it. Also I think this code can be set if you are running tall tires and dont have the right gearing not sure about that tho.:dunno:
     
  13. dirtwarrior17

    dirtwarrior17 Banned

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    I was asking because my rig has a mechanical with 35's and it ran great until i lost a main.
     
  14. bad_bo_ti

    bad_bo_ti 1/2 ton status

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    i will check the vss sender i did have the transfercase out of it 2 months ago (dont drive it that much) as far as electronic spark i think i will do as stated above, check timing them pull cable and resest codes and see if they come back. and maybe start looking for a different distributor. thanks, chris
     
  15. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Yes, 42 is EST circut. Either: the PROMs not seated, wirings bad, or the modules bad. I can tell you how to check it, PM if you want.
     

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