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Thread: No Spark # 7

  1. #21

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    Quote Originally Posted by j cat View Post
    so with that then remove get access to the PCM check all wires there and remove connectors to inspect for damage/corroded green wires/ rodent chewed etc..
    Yeah, there is no green/damaged pins when I unplug the PCM and I can see no chaffing or rubbed wires. Called around for a used PCM but they said it had to be programed at the dealership. Really hate to have to go the stealership. :(

  2. #22
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    the wires at the coil to the pcm trace them back to the PCM connector [pin]. then use an OHM meter to see if the wire is good. if these 2 wires are good then it may be the PCM.

    this is an odd ball failure if so.

    report back what actually fixed it...

    also I would put it all back to see if the miss is gone... would not be the first time a weird problem electrical like this got fixed just by messing with the wire harness/connectors.

  3. #23

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    Quote Originally Posted by j cat View Post
    the wires at the coil to the pcm trace them back to the PCM connector [pin]. then use an OHM meter to see if the wire is good. if these 2 wires are good then it may be the PCM.

    this is an odd ball failure if so.

    report back what actually fixed it...

    also I would put it all back to see if the miss is gone... would not be the first time a weird problem electrical like this got fixed just by messing with the wire harness/connectors.
    I found this picture of the coils, looks like all the "B" wires are tied together so now I just need to figure out which pin is 72 on the PCM plug.

    - - - Updated - - -

    I didn't really want to, but I split the harness open and followed the wire (which turns orange at the coil harness to main harness) all the way to the PCM. I don't have a probe small enough to check the connection but I did test it about an inch back and have continuity to there, so I'm leaning towards the PCM t this point.

    - - - Updated - - -

    *EDIT* I pulled the back off the PCM (which was difficult!) and counting the wires probed the 9th soldered connection on the back of the circuit board to the red wire on the coil plug and it does have continuity, so just ordered a used PCM for $50.00. Will report back if this cures it.
    Attached Thumbnails Attached Thumbnails Ignition Controls - Ignition System Coils 1,3,5,7.jpg  

  4. #24

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    Quote Originally Posted by Rukee View Post
    I found this picture of the coils, looks like all the "B" wires are tied together so now I just need to figure out which pin is 72 on the PCM plug.

    - - - Updated - - -

    I didn't really want to, but I split the harness open and followed the wire (which turns orange at the coil harness to main harness) all the way to the PCM. I don't have a probe small enough to check the connection but I did test it about an inch back and have continuity to there, so I'm leaning towards the PCM t this point.

    - - - Updated - - -

    *EDIT* I pulled the back off the PCM (which was difficult!) and counting the wires probed the 9th soldered connection on the back of the circuit board to the red wire on the coil plug and it does have continuity, so just ordered a used PCM for $50.00. Will report back if this cures it.
    So, are you going to install the used pcm and then have it towed to a dealer for reprogramming? Before you go thru all that you may want to call your dealer and see if a flash update is available for your pcm. Sometimes they install the update for free. it might solve the issue

    1995 Silverado 4x4
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  5. #25

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    Quote Originally Posted by Pikey View Post
    So, are you going to install the used pcm and then have it towed to a dealer for reprogramming? Before you go thru all that you may want to call your dealer and see if a flash update is available for your pcm. Sometimes they install the update for free. it might solve the issue
    I'm F***ed anyway. When I pried the back off the PCM I must have damaged it somehow cause now it won't crank over. :(

  6. #26

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    Quote Originally Posted by Rukee View Post
    I'm F***ed anyway. When I pried the back off the PCM I must have damaged it somehow cause now it won't crank over. :(
    I would try disconnecting the battery for 15 minutes. You may have triggered the security system

  7. #27

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    Quote Originally Posted by Pikey View Post
    I would try disconnecting the battery for 15 minutes. You may have triggered the security system
    okay, worth a shot, thanks.

  8. #28
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    Quote Originally Posted by Rukee View Post
    I found this picture of the coils, looks like all the "B" wires are tied together so now I just need to figure out which pin is 72 on the PCM plug.

    - - - Updated - - -

    I didn't really want to, but I split the harness open and followed the wire (which turns orange at the coil harness to main harness) all the way to the PCM. I don't have a probe small enough to check the connection but I did test it about an inch back and have continuity to there, so I'm leaning towards the PCM t this point.

    - - - Updated - - -

    *EDIT* I pulled the back off the PCM (which was difficult!) and counting the wires probed the 9th soldered connection on the back of the circuit board to the red wire on the coil plug and it does have continuity, so just ordered a used PCM for $50.00. Will report back if this cures it.
    make sure the #7 b wire goes to the #!,3.5 b coils pin connection

    there are people that program PCM ..some guy I saw does this work for about a hundred or so. dealership would be an easier way to handle it.

  9. #29

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    Can I just plug in the used PCM and drive it to the dealer for programming?

  10. #30

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    Quote Originally Posted by Rukee View Post
    Can I just plug in the used PCM and drive it to the dealer for programming?

    I don't know what controls the security system on that truck. It could be the pcm. I think that the radio and some other things are locked to the vin, so those will not work. I know, not a big deal. But, to be honest, I dont know if it is even going to start with the used pcm.

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