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Old 03-11-2013, 02:10 PM   #11
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so go to the plug and if it looks like the plug on that link test a to e the trans should be 20 to 40 ohms. check a to case should be many or infinite. the truck side should be 12v on a and e. the pcm monitors circuits that are ground controlled by putting 12v on the line and monitoring. then when the circuit is activated it gets grounded.
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Old 03-11-2013, 02:42 PM   #12
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Will do, thank you for the advice. Much appreciated!
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Old 03-11-2013, 03:28 PM   #13
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let us know how you make out
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Old 04-08-2013, 07:13 PM   #14
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@jwfirebird appologies for the delay, as the truck runs and shifts fine I have to find downtime to do the testing. First of all thank you for all your assistance and info. Yes I too believe that this trans is the 4l60e although all of my paperwork states otherwise. A couple items have transpired over the last couple weeks. First of all I was able to do some ohm testing of the wires and based on your feedback of testing the resistance between pin'* a and e I only ended up with a "1" reading however a to trans case was 13xx something. I also checked out the "brown" wire further and it was indeed pinched (the wire is for the EPC force motor connection) so I went ahead and replaced the harness. Unfortunately the P0753 code came back. I have been trying to find a diagram/pinout to go from the PCM back and try to figure it out that way but haven't had much luck (the ones I did find didn't seem to match up with the number of pins) not sure if you may be able to point me in the right direction there? Any other recommendations would be greatly appreciated. I doubt it'* related but thought I would throw it out there as well this truck "previously" was running a P0420 code but both cats tested fine and I haven't seen the code in a few months. Just in case I figured I'd add the info. Thanks again.

I should also note that the readings were from the plug to the trans not from internal trans as I had "hoped" the harness replacement would solve the issue.
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Old 04-09-2013, 08:15 AM   #15
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did your readings change to the case after the harness?

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Old 04-09-2013, 02:34 PM   #16
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Thanks for the reply, I'm not 100% on your question "did your readings change to the case after the harness". Unfortunately I didn't think (bad on my part) to test inside the trans after I replaced the harness. The resistance tests were at the plug to the tranny (but on the outside). I did get a "many" ready when going from pin A to the case as you had mentioned I should. It was the A to E test that came back with just a 1. Which if I understand correctly means that it is a higher ohm than my 200k setting or something of the sort. I wasn't using a wire probe or anything of the more accurate nature either, just the 7 Function Digital Multimeter pins. Hope that makes sense.

I guess some of my confusion (if I wasn't confused before I am now with the diagram). The first one you sent me MegaShift 4L60E, didn't seem to match up (Under the GPIO/4L60E External Wiring Diagram) to any of the plugs that I could see going from the trans harness to the ECM. Now in the most recent diagram I don't see if this is the Red, White, Black or Blue plug from the ECM? I was looking at this pin out which shows the 1-2 shift solenoid (which I believe is solenoid A) at pin 6 of the red ecm plug. Just not sure if that is accurate based on the other images sent. Thanks again, your help is greatly appreciated!
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Old 04-09-2013, 04:57 PM   #17
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i would believe that one you got more than the one i have.they are frequently wrong because it will be good for one year and they wont change it.

back to your problem then, i thought you meant 1, but that is really infinite. or I. so you measured a to e on the truck side but what i meant was on the trans side. if you measure a to e in the trans you should get 20 to 30 ohms. and if you measure a to case should be infinite or very high, just want to make sure thats what you are saying
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Old 04-09-2013, 05:17 PM   #18
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Yea I understand the measurements for the trans side, unfortunately I didn't test it when I replaced the harness and it'* all closed back up (definitely my mistake there, assuming gets me every time). I'll crack again if necessary but I (hopefully) feel confident with having replaced the harness and both solenoids that the issue will be outside of the trans from the ECM to the trans harness plug wiring. It'* just to figure out my way from the ECM to the trans harness plug through the splits, etc to find it. Seems how the truck runs and shifts fine, I doubt its possible that the wire has a short or is being ground out right? It'* obvious the power (e) is good because I'd imagine that I would get other codes as well such as Solenoid b, etc and likely be in LIMP mode. So if I understand all of this "correctly" I'm imagining that my 1-2 Solenoid A wire (a in the plug) is causing the reading inaccuracy due to resistance? or possibly the ECM is bad? I'm not the most experienced especially with wiring so all of your help is much appreciated.
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Old 04-10-2013, 07:35 AM   #19
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right so if you take the pcm red c2 connector off and look for the lt green at pin 6 if your pin out is correct you should be able to check resistance from there to the trans plug at that pin and get very low and shake the connector make sure you dont have loose wires. i think while i was down there i would check the trans side to be sure i didnt get bad new stuff. ive screwed myself believing just because its new its good before
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Old 09-23-2013, 02:06 PM   #20
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Apologies for not posting sooner, thank you again for all of your help in the matter. After having replaced both Solenoids as well as the pinched harness additional testing as you pointed out showed that it was possible my PCM was bad. I purchased a used/flashed module off of ebay. Installed it and although I had to get a dealer to do the CKP relearn procedure all is well now. No check engine, shifting like a dream. Thanks again for all the help, it is very much appreciated!
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