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3 buses SCI CCD J1939 SCI: is used for troubleshooting and talking from the obd plug to the ecm and pcm. This is nothing more than a obd compliance bus in my mind.
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JTEC refers to the controller, PCM.
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however I think the likely issue is just a shotty rebuild of the ecm. AC noise shouldn't fry the ecm that fast. I would replace the alternator if you are seeing a ton of ac noise for go
To start I have a 99, 2500, Auto, 2x4, 211,000, Lift pump in tank with Relay, 275 HP Bosch Injectors.
I am the second owner & got the truck in 2001, IIRC it has 15,000 on it.
To make a long story short, I just finished doing a bunch of things I have been putting off for too long now.
Recently replaced (in order of installation):
Vacuum pump (http://www.fixinrams.com/)
PS Pump (https://www.genosgarage.com/) & Hoses (https://ormebrothers.com/).
Brand new Bosch 275 HP Injectors (Had Edge Jammer Stage 1's & wanted to see the difference)
ECM from https://carcomputerexchange.com/ (Lift pump was not turning on reliably & WTS light was acting all wonky)
Fuel Filter housing for 00-02 Cummins https://www.genosgarage.com/product/dodge-ram-cummins-replacement-fuel-filter-cannister-gg-fc98599/360 I was trying to troubleshoot the lift pump driver issue in ECM & Manged to crack the 99 Housing, so $180 later here I am....
VP44 from https://www.bluechipdiesel.com/ (This is the second VP44 I have put onto the truck, the first very early in life, due to dead Lift pump)
So here is the deal. As I mentioned Ive owned this truck pretty much its entire life & have put just about every mile on it. I had the vacuum pump, PS pump & injectors put into it by a local Dodge shop, because I did not have the time to take care of it. no issues/worries with that.
off & on for the last year or so I was having issues with the ECM turning the lift pump on. I dug into it a bit & called the folks @ Blue Chip & Doug suggested that I just run the lift pump off of the Wiper circuit (as its hot during "run", but not "start"). while that worked fine (the truck would start & run every time), once of the side effects was that I was getting a P0230 code. I called Blue Chip back & he said that is because I did not have a load on the ECM (because the lift pump was disconnected) & that I should just "stick a fan on it to blow across the Inj pump" so that the ECM would see the load. I didn't like that idea, so I wired another relay on that output (the exact same relay that I am using for the lift pump) & much to my surprise that did not resolve the issue.
I did a bit of research & called 6 or 7 ECM sources & found that car computer exchange seemed to be knowledgeable about the Cummins specific issues & had a good answer to each of my questions (Im a Manufacturing Engineer for a company that produces devices that measure air pollution). They were waiting on cores & said if I return mine I would get it quicker than if I waited to order one & then send my core back later. So I did that.
I replaced the ECM & fuel filter housing @ one time & rewired the Lift pump back to the ECM where it should be. every few years I check all of my grounds to make sure that there is no corrosion (like we get any weather in San Diego, right...............) & that everything looks ok. I purged all of the air out & fired up the truck & it fired up after a little cranking. HOWEVER......... the CEL came back on again. I hooked up the scan tool, cleared it & fired it back up again. no more CEL. Yes I did something stupid............. I did not read the code(s) I just cleared it/them.
I replaced the Injection pump & when I went to fire it up, I found the batteries were on their way out (slow cranking & no fire). they were 5 years old so I replaced them. Hit the key with the new batteries & it cranked over great & fired right up. HOWEVER the CEL is back on again.
I broke out the $10 China Freight scanner & it came back with "there are no codes" (yes the CEL is on) This is not the first time this has happened. So I broke out the OTC Genisys, & the freaken thing wont talk with the stupid truck. This is not the first time this has happened over the last 8 or 9 years. Ive had this issue off & on for a while. Ive not cared because the truck has worked fine & not had any CEL's so why would I care (paying for that now..............).
Here is where it gets weird. If I use the HF scanner & force it to clear the CEL it will do it. if I ask the OTC to clear the CEL, it will not. neither of which will "get data from the truck". the CEL comes back on just about every time I try to start the truck. Ive cleared & started it 20 or 25 times since I replaced the Inj pump & most of the time the CEL comes back on. I have tried a few things. like checking connections & Grounds & other such things to figure it out, clear the CEL & fired it up & it comes back on........
MORE....................
So........ the questions.......
I have a factory manual & have dug into the schematics & see that there appear to be 2 Comm buses. once is the CCD & the other is the SCI.
I have read a bunch of stuff on this site as well other places, but am kind of confused about how this works & what does what.
as much as anything Im trying to learn with these questions, not to just fix my problem, so bear with me.
I get that the CCD talks between the ECM, Timer, Dash, PCM, etc to transfer information from one place to the next. it is also present on the ALDL so I would assume that a "scanner" can talk on the buss as well to get data out.
It appears that the ECM & PCM are connected to the ALDL on pins 6, 7 & 14. Its interesting to me that there is a single transmit line shared between both computers, but they each have separate receive lines.
SO............... When I hook up my scan tool cheap *** scan tool what is it talking with? the ECM? through the SCI lines or the CCD?
When Im using my OTC & turning on & off the AC Clutch, Trans Solenoids, lift pump, etc. what buss is it using?
When there is a code that the trans is not working correctly, where is that coming from? is the scan tool talking with the ECM via the SCI & its getting the codes from the PCM through the CCD? How the heck does this work.........
Shoot........... I didn't want everything in one HUGE post............
So, Specifically to this problem.
How do I go about troubleshooting my communication issue? I took the OTC & plugged it into my wifes Mercury & it allows me to see everything & do everything, its working correctly.
I have had issues with the Truck talking to scanners before, but Ive also had it work just fine & allow me to turn on the trans stuff & to datalog ECM & PCM stuff & watch the APPS voltage go up & down & everything you would think it should be able to do. so I know that it has worked before.
IMO, I need to get the scanner working before I can figure out why the CEL is on. I suppose I could assume that its the same P0230 code, but I dont want to assume anything...........
thanks folks.
Bob
Edited by Bobalos