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Edge CTS2 causing CEL?

13K views 22 replies 8 participants last post by  mizterwizard 
#1 ·
Hi all. So i'm having a bit of an issue. I just got my CTS2 back from warranty for a cracked screen and as soon as i plugged it in my truck went nuts. Stablitrak, trailer and one other pop up on the dash appeared and then threw a U0073 code. Which is lost communication to bus i believe. If i leave it alone and cycle the ignition 4 or 5 times, the cel clears but it seems to come back intermittently. Also when it happens the, the CTS2 boots weird. As in the normal screen(background screen customization) isn't there and only has 2 PIDs showing. I unplug it and the CTS2 boots ok, restart truck and the CEL is there. Thats when I cycle ignition few times to clear it. It didnt do it before i warrantied it but i did have one stabilitrak popup and U0101(lost communication to TCM module) code but the CTS2 wasnt even plugged in at the time as it was broken. But I dont remember if the cable was plugged into the OBDII port or not when that U0101 code popped up. So Im wondering if it's my truck, the CTS2 or maybe even the cable thats screwing things up?
Anybody have any ideas? It's driving me insane



2017 GMC sierra 2500
 
#3 · (Edited)
The way the buss works is that one of the modules (probably the BCM or ECM) supplies 5 volts to the buss wires. +5V on one wire and -5V on the other. This is just a voltage. There is almost no current available so anything that disrupts the buss will kill the voltage. Each module on the buss, including the one that is supplying the voltage, has the ability to ground or not ground the 5 volts. That causes the voltage to cycle between 5 and 0 volts. They do this very fast and it creates a signal on the buss. If there is an extraneous voltage, ground or cross circuit in the buss it will mess up the signaling and stop communications over the buss. That will prevent important information from getting to where it needs to be and set a U code.

First thing to do is to put everything back to stock and see if it still has problems. If it all goes away then send the CTS back and tell them to fix it right this time. If it still has the problem then you have a buss problem or the module that supplies voltage to the buss is bad.

If the buss is bad then you need to test for a short to ground, power or another wire. The most common problem is a short to ground caused by a pinched or rubbed through wire. You may need to unplug every module on the buss to get a good reading on a short to power or ground. If you do that and find nothing then the problem is probably a module. Plug them back in one at a time and see which one kills the buss. There is no easy repair for a bad module that the average person can do. It has to be rebuilt by a specialty shop or replaced.

If you decide it must be a module then the one that is having the most trouble communicating is likely to be the problem. If there are several that can't be reached then the one closest to the diagnostic connector is likely to be the problem. If that is no help then the one that is closest to the connector that you can't scan is likely to be the problem. You will need a diagram of your buss showing how it is wired so that you will know what is near and what is far electrically.

This isn't an easy diagnosis. It takes time, patience and a little luck wouldn't hurt either.

If you find that removing the CTS fixes the problem then the cable is a very likely cause. The easiest test would be to substitute a known good cable. If you know someone with a similar setup then that would be the best way to go. If you are on your own the best thing is to test each wire in the cable from end to end for continuity and shorts to other wires. The trouble is, wire problems are often intermittent. It's really hard to find a problem that isn't there right now.

It is also possible that the CTS itself is the problem. Perhaps when they were replacing the screen thy got a dob of solder on the connections for the cable inside or maybe something conductive is just rolling around inside there. I would think this is the least likely source of a problem but if it happened right after having the CTS fixed then that raises the probability considerably.
 
#4 ·
I would definitely pull the CTS2 and cable for awhile and see if the problem appears without them in place, if so I would suspect the cable since you had a problem once with the CTS2 out but the cable still in place.

Anything plugged into the OBD-II port can cause these sorts of failures if it has an issue or simply doesn't play nicely with the vehicle communications. I have a 2016 Corvette Z06 equipped with the 8 speed (8L90) automatic and GM uses their lousy AFM/V4 fuel management system on these cars causing the engine to go into V4 mode under light load. That wouldn't be too bad EXCEPT in order to reduce the vibration from operating a V8 in 4 cylinder mode the lockup clutch in the torque converter is continuously modulated off and on to absorb some of the excess vibration and this leads to accelerated wear of the converter clutch followed by RPM variation at cruising speed quickly followed by severe driveline shudder. The ways to avoid this are to either set the transmission to manual mode which disables V4 operation or use the Range anti-AFM module which plugs into the OBD-II port and inhibits V4 mode. It took several revisions for Range to come up with a version that didn't intermittently cause a communications error between the ECM and TCM at startup which resulted in a CEL and the transmission being locked in 4th gear in the forward range. The cure was to restart with the Range module removed and now Range does have a working version that doesn't create these communications errors but in the interim I used a switched OBD-II extension cable that allowed me to turn the Range module on after the initial startup communications had slowed.

I am ordering a 2018 Denali 3500 SRW shortly and I am planning on getting a CTS2 for it to monitor regens among other things. After my experience with Range I was a little leery of leaving anything plugged into the OBD-II port but your report is the first I have seen of CTS monitor related issues. For curiosity does having the CTS2 monitor plugged in interfere with OnStar collecting its monthly data or running diagnostics on demand? The Range module has to be unplugged for these activities but it is doing more than simply reading sensor values.
 
#5 ·
hmmm good info. I have left it unplugged for awhile and no codes were thrown. But It's only been a couple of days since i got my CTS back so i don't have enough driving on to say one way or the other for sure. But the little i have messed with it, it sure seems like it's CTS2 or cable related. It's funny you mentioned the onstar because i called in twice for codes and both times they couldn't get a signal back. I didn't mention the CTS2 to them but they had me restart truck and i made sure it was unplugged while it was off. When it started next they could get a signal.
 
#8 ·
So I may have solved it. I narrowed in down to the OBDII connector. When i wiggled it, it would cause truck to freak out. Thought it was the cable until I looked closer at the port itself. I think one of the GM techs might have buggered it up a bit when i took it in for the recall couple weeks ago. The pins seem pretty loose in the plug itself. I've tested it a bit more now and it *seems* to be ok if i push the wires from behind while plugging in the cable. I'm hoping all it was, was a bad connection. I'll post a video of the plug. I'm curious if other guys trucks ports are like this?


https://youtu.be/H0JiD-Bvnq4
 
#9 ·
The pins seem tight in my 2006 GMC and 2016 Corvette so I don't think they should have that much free play but have someone with a current model pickup chime in to be sure because it could just be a cheaper connector being used now.

There is usually a plate that is part of and at the rear of the connector body that locks the pins in place as a group and maybe this isn't seated all of the way in your connector. Other electrical connectors are set up where each pin locks mechanically in its slot but heavier connectors that are likely to see somewhat frequent insertion/removal usually have the more robust backing plate system.

In general the OBD II port doesn't stand up well to a lot of use and the typical design thought would be around 100-200 uses over the life of the vehicle. Usually the wear shows up first through loss of socket contact tension. It is best to buy a short extension cable and leave that permanently plugged into the vehicle OBD II connector and then any wear occurs to the easily replaceable extension. That is what most of us using Range modules do to avoid OBD-II port connector wear and I use a power switched one since older versions of the Range module drew power even with the vehicle off leading to a drained battery.

You should be able to get an extension cable at any auto parts store or more conveniently via Amazon which is where I bought mine a couple of years ago.
 
#10 · (Edited)
I hate to burst your bubble but the video shows a normal situation. The OBDII connector is built kind of loose because so many things get plugged into it.

Try taking it loose from the truck and see if you can make any of the terminals touch each other. The pins that count are 1, 3, 6, 11 and 14. These are all data lines. 16 is battery power. 4 and 5 are grounds. The rest are unused on most trucks. If the data lines can touch each other or the power and ground wires then that would kill the buss. I suspect if you look up the wires from the connector toward the main harness you will find a problem with the wires that your fiddling corrected by moving the wires slightly.

I was pretty sure the problem was in the CTS connector harness but maybe not.


Quote: wq93
There is usually a plate that is part of and at the rear of the connector body that locks the pins in place as a group and maybe this isn't seated all of the way in your connector. Other electrical connectors are set up where each pin locks mechanically in its slot but heavier connectors that are likely to see somewhat frequent insertion/removal usually have the more robust backing plate system.


That is true but not always. It's worth a look.
 
#11 ·
GM techs no longer need to use the OBDII port to access ECM.

Watched them do my TPMS change via wi-fi from their laptop.

(of course there could be 2 ways to access, but if they need the laptop software for programming anyway it seems like using a cable would be redundant)
 
#12 ·
Quick update. I've 100+ kms on today and no issues. It would normally mess up before i got around the block. Fingers crossed that was the problem. Thx for the help wq93 and mizterwizard. Also I took your advice and gave the wires a good going over and it seems to be ok. I'm going to file away this useful for sure in case i need it.
Thanks guys.
 
#13 ·
So it looks like I'm still up $hit creek. After a few days last time i had another small hiccup so I ended up sending it back to edge to have it looked at. They said it tested fine. i just got it back and now it's the worst it's been and I'm reaching the end of my rope with this thing. Do you guys have any suggestions what to look at next before i throw it in the garbage?

Video of what its doing now
 
#14 ·
Wow, that's some crazy stuff there. The only problem I have had with my CTS2 is sometimes it won't turn on when I use remote start and get in and turn the key. When that happens I turn the truck of and restart and everything is fine.

Good luck with this!
 
#19 ·
Mine has been on for at least 6000 miles no issues, I did update it and had to re- input all the info, I would unplug from OBD port drive around a little plug back in and input all the information again. If you accidentally put wrong vehicle in that could cause issues
 
#20 ·
have you tried to replace the chord?
 
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