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Help! Serial data bus issues, PLEASE HELP!

Jesse Johnson

New member
Oct 2, 2023
Hello everyone, I hope that you all are well. I also hope that I don’t offend anyone being this is my first ever post on the forum and i’m asking for help, but i’m at a loss trying to solve this issue. Basically I am having what appears to be a complete serial data bus malfunction. Gas gauge pinged at 0 even though I know there’s gas in it, coolant temp maxed out oil pressure at 0 only gauge not going crazy is the battery voltage gauge. The gauges sweep as normal upon startup as well. Codes as of right now are as follows

PCM - No codes
TCM - C1255 H | U1255 H C
RTD - No codes
BCM - U1255 H C | U1016 H
IPC - U1016 H
Radio - U1016 H
HVAC - No codes
LDCM - No codes
RDCM - No codes
SCM - No codes
BO-RFA - U1016 H C

These codes aren’t always the same, sometimes every module shows U1016 as a current code. The only codes I’ve noticed that are consistent is the U1016 H C code for the BO-RFA and the U1255 H C code for TCS and BCM modules.

I installed a catback exhaust and intake manifold shortly before all of this but everything was good and I didn’t have any issues for about 2 to 3 weeks. So I’m not sure if that has any correlation to the issue that I’m having. So far things I’ve done to the car is I’ve checked grounds in the engine bay, I then sent It to a shop where they checked for shorts to the pcm or bcm and their respective grounds and found nothing. They also replaced the bcm and the issue still persisted. I replaced the battery and ignition switch, still the same issue. Checked fuses to the bcm and pcm and they were getting power as they should. I disconnected the star connector that has the door and seat module to isolate them, didn’t fix the issue. I then went out and bought a scope and a connector tool with a bunch of probes spliced together, so that I could add each module back onto the network one at a time while monitoring their data. I had hoped to find the module that’s either pulling the data bus up high or down low. To my surprise after measuring dlc pin 2 (serial data wire) and after connecting each module one by one at the star connector, it showed a 7 volt square wave pattern. Meaning communication on the bus is as it should be. While doing this I found that the pcm isn’t putting any data out on the bus. The bcm is putting data out but it’s very very slow. And the IPC bombards the bus with data like 3x more than any other module and I’m not sure if thats normal. I then tried to jump the pcm and the bcm and I get no comm, I only get communication with those two modules when I add the ipc to the network aswell. But I know that jumping the pcm and bcm should work unless there is a fault with either of the two modules, but I’ve ruled out the bcm seeing as it was replaced and the issue persisted, and also I would expect a few no comm messages on the dic if it was a bad bcm. So here’s where I’m confused, if it was the pcm wouldn’t I be getting a no comm at the pcm when all of the modules are connected? The pcm communicates but throws no codes, in fact it’s the only module that hasn’t thrown a code, history or current. Also if it was an issue with the pcm, why can I connect to it with a scan tool? So it isn’t a ground issue, isn’t the battery, ignition switch, bcm or any other module taking down the bus. What else could it be if not the pcm? And more importantly, how can I be having a serial data bus malfunction if the data bus isn’t shorted to ground or power? Any help would be greatly appreciated.

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