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PCM communications issue
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Post PCM communications issue 
This is s 97 C2500 with a 7.4 Vortec stock PCM.

Had to replace the plastic distributor due to an ear breaking off.

The mechanic that did it for me (don't currently have a working scantool to reset timing) was unable to get their scanners SnapOn Mt2500 and Snapon Solus and another newer non-Snapon they had for demo was able to get all of the scanners to pull codes. The scanners are showing that timing needs to be set. None of the scanners are able to communicate with the PCM to do any diagnostics other than code reading and will not connect to do a timing learn.

Wiring from OBDII plug to PCM ohmed out fine.

Replacement PCM has been installed, cleared up most of the rough run but still has timing code.

Any suggestions?

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I am surprised none of the Snap-on tools work. I cannot remember the part Number for the Snap-on scan tool, that one of my bosses has. You could set the campret with it. Not sure about a crank relearn like we do with our EFI live V2 scan tool. I do no the EFI live will not work on the 97 pcm. Not sure what to tell you on this.

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You can make the code go away by setting the distributor correctly. I have done it many times without the scan tool looking at the cam sensor/distributor PID.

Put on true TDC #1 compression stroke remove the distributor cap and make sure that the rotor is pointing to the contact inside the cap connected to the #1 spark plug wire. Once this is almost directly inline you can twist the distributor "very very very slightly" in each direction to find the sweet spot and restart motor to see if code comes back.

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It's a busy shop that was doing the work. The newer SnapOn scanner would have all the current updates and has been used on numerous vehicles in addition to mine.

The crank sensor was replaced and he is sure he has everything manually set.

The bigger concern is there being no communication between 3 different scanners in diagnostic mode with 2 different computers.

The truck appeared to run fine on the trip home with it last night. I need to be able to haul with the truck, I don't need the truck to go into limp mode with a load of hay or the tractor behind it.

I plan on doing the 411 swap at some point later this summer.

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I can tell you from personal experience that I will never put anything but a GM CPS into one of my motors again. The aftermarket ones have no quality control or consistency - they also scatter at higher RPM. I had one throwing misfires over 4k for a long time I couldn't figure out until I started watching sensor input on an AutoTap. Just a thought...

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Those CKP(CranKshaft Position) sensors can be very picky on how you install them. Be sure to push it in, THEN tighten down the screw. I had thought I had pushed the sensor in all the way, but it wasn't and it must have cocked in there slightly before I tightened her down.
I can see why GM didn't stick with this design.

peace
Hog

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The CPS appears to be functioning properly as installed.

I'm more concerned with their being no communication between scanners and computer except for code reading.

Anyone else with this problem or any ideas what to do to get the communication working.

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I'm using an MT2500 and crank relearn and setting distributor timing was already part of my 'old' 1999 (MT25001099) cartidges. I now have the latest update available 2007 cartriges too.

I wonder if they were using the correct 'personality key' (=connector cable adapter key). You said it was a busy shop and since the newer Snap-On scanners do NOT require a 'personality key' (so the shop may not have used it for years), it is possible they simply have not thought about to use it with the MT2500 scanner, which requires this adapter key).

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They used the Brick, the Newer Snapon Scanner and a new scanner by another company. None of them would communicate beyond code reading.

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