Mark Robles

Can anyone reply with the Computer Data Lines Circuit Schematic/Diagram for the 2011 Chevrolet Suburban 5.3. Like a snapshot or file. Messing with some UXXX codes, more specifically U0073.

tech2

I look one up for you. Which bus as there are more than one. which modules are the codes set in and which module is offline?

Mark Robles

It's giving me P069E and U0073. My gauges will intermittently go erratic, door locks will lock repeatedly (not really unlock just constantly lock), weird clicking under the dash, and the transmission will thump when changing gears. Weirdly it will only do those things when the gauges act sporadic, but it will drive normally if the gauges act normal. The battery shows 15 volts all the time even when the truck acts up and 13 volts when off. I'm going to drive the truck more to see what other codes pop out but I don't have an expensive scan tool to check each specific module. I've taken it to the dealer and they informed me to change all 4 battery cables (3 positive, 1 negative) and the Electronic Suspension Control Module (ESC). I've replaced the negative cable, positive cable to the fuse box, and the mega fuse. I doubt it's the starter or alternator cable. I have no idea to tell if the ESC module is actually bad or not so I'm hesitant to spend $700 on a unit if I don't need it. Especially if it's not actually bad and it's just failing to communicate. Judging by the codes I'm assuming there is a fault, most likely, an open circuit or failed module on the High-Speed LAN (CAN High). But I would appreciate it if I could get the schematic of both the low and high (I think they're both intertwined in the same diagram anyway). Also, to answer your other question, I believe multiple modules go offline when the truck goes possessed. TCM because of the thump, BCM because of trouble starting and locks acting up and it not wanting to start intermittently as well. ECM because I think the engine goes into like a limp mode losing power essentially.

And on top of this, all of this didn't start happening until after I took my truck to a personal mechanic because the gas pump would keep shutting off whenever I filled up. Got my truck back and bam all of these issues popped out of nowhere.

repairman54

Suspension module is above the spare tire. Fuel pump module is also in the rear. I'd check the grounds back there as it is a rust prone area.
Since someone was messing around in that area those modules may share a common ground point. Especially if a bump triggers a problem something may be loose.
alldatadiy.com is my source for a shop manual that will show all the power and ground points. Cost is a lot less than an hour of shop time.

tech2

having issues pasting the link.
when you do get a diagram first thing i would check is the termination resistance of the bus lines. all testing should be done when the fault is present. You do need to know what modules the codes are setting in and for what module they say is offline.
the termination resistance should be 60ohms. disconnect the battery and measure across pins 6and 14 at the dlc connector.

Mark Robles

Hey, Thanks for all the help so far guys. I really appreciate it. repairman54, I checked underneath the truck and didn't find any noticeable ground wires or ground points just in my face. Also, the truck is extremely clean with zero rust, because it's a Texas truck. I doubt it's a bad ground for one of those modules because it seems like the whole Can High network goes offline when the system goes haywire not just those two modules. Also, no exact driving characteristic "triggers" the issues it just seems to happen randomly usually less than 10 minutes after first starting. I also drove the truck more today to see if any new codes will come up and it sure did.
The codes were:
P069E
U0100
C0301
P0700
Yesterdays Codes:
P069E
U0073
Also, when I was trying to scan the obd it seemed like my scan tool would just freeze halfway, I had to keep turning the truck in the on and off position and disconnecting the obd reader until it started actually scanning. The truck still does all the weird things I mentioned in my first post. It also shows the following messages on the tiny info screen: "Service Stabiltrak", "Service Trailer Brake System", "Service Suspension System", and "Service Traction Control". The check engine light and traction control light stay on the entire time as I'm driving but it seems like the abs light will pop up sporadically.
In reply to tech2, I measured the resistance across pins 6 and 14 and it showed 114.5 ohms. So I think it's sure-fire I have a Can-Bus issue. I'm assuming Can-High because the modules affected are correlating with the High Network. I'm not totally sure what to do from here, getting the computer data lines schematic is definitely the first thing but are there any hints or jobs you guys have dealt with that can help me with my diagnosis. The more I learn about this truck's problems I feel like the further away I am from the solution lol. I'm gonna try to stay as active as possible on this thread until I hopefully find the issue and help others who are experiencing the same issue as me.

repairman54

Here's a small sample of the grounds in my Tahoe. There are a lot of them. You don't need to be in the salt zone to have ground issues, rain will do the same. It could be a main ground under the hood. I've had good looking cables be bad or poor engine to frame jumpers having issues. A good electronic connection cleaner/lubricant spray is a must for all the connectors. Late '00 and early teen's GM are known for fretting corrosion issues in harness connectors. My '09 Malibu suffered from that, they even had a recall for BCM connector issues.
Image won't open now.

tech2

lost of com issues can be from damaged bus wires, bad modules and loss of power and grd to the module. to narrow down the search....find out which module is off line and test that module power and grd.

Mark Robles

Partial Solution:
Sorry for the inactivity, pushed my burban on the backburner to focus on other things. I finally caved into looking at the Electronic Suspension Control (ESC) Module. For some reason, I just couldn't fathom thinking that a bad suspension module was causing my truck to go into a horrible limp mode. I unplugged the module and realized that the plug was way too loose for some reason like it wasn't fully seated, I don't why it was loose. But my dad and I jumped the two tan and tan/black wires on the ESCM plug and we finally saw what we were looking for. We measured 60 Ohms from the ALDL (OBD2 port). We left it unplugged and other than the service suspension system message, traction control, and abs light being on (which I expect) the truck now FINALLY drives normal. We haven't plugged it back in to see if it was just a loose connection or if the module is actually bad like the dealer said but MAN am I happy.

Now my question is can I buy a used module and reflash it? or do I have to buy a new module and then get it reflashed? If I could buy a used one it will definitely be a whole heck of a lot cheaper. But I also want to thank repairman54 and tech2, you guys definitely helped a lot with the diagnosis.

repairman54

I'm not sure on a used module needing a flash or being swappable.