I had a new CAN issue so up about a week ago, right after replacing my fan clutch. Anyways, I was driving home from work and the tow/haul light started to flash, and the RPMs jumped to about 2000 and a slight loss of power. The issue cleared itself up before I could pull over to just for codes. At first when I tired to read codes forscan said there was no comms with multiple modules. I tried to read them a few time and was final able to get the following codes U0074, U0100, U0155 and U1900. I cleared them and it happened 1 more time on the way home with the same results. It has happened randomly 2 or 3 times since, but with one additional symptom the TBC fault flashes on my message center. Each time it clears itself up within a few seconds. I went camping last week and didn't have any issues with towing, but one time while driving unloaded it did it again. So any ideas on where to start looking, the fan clutch isn't on the CAN network but can it cause this type of issue?

 

When you get issues on the CAN bus lots of times a module is failing.
There are some simple tests that can be done with a DMM. I'll have to
find the PDF and post it.
Well I did not find the CAN bus one but I did find the TBC PDF.

 

I just want to give an update, since these types of threads pop up once in a while. I tested my CAN network and couldn't find any issues, and I was able to communicate with all the modules on the network.

I have been driving without my OBD2 dongle connected for the last couple weeks and haven't had issues. In searching the internet, I found a few references to the dongle maybe causing network issues.

As a side note while running Torque Pro on my phone I would lose communication and or have difficulty connecting to the truck. Usually that would resolve be unplugging and plugging the dongle back into the truck. I did just send a message off to the manufacturer about any testing procedures for the dongle. We will see.. Maybe I'll just get a new one and see what happens.

 

Sometimes a fan clutch issue can affect the PCM voltage, which in turn can affect module communications. Everything OK with FICM VPower and LPower?

Might want to verify the buffered 12V power at the fan clutch connector - Brown w/ light-green wire IIRC. The wiring manual labels it as reference voltage, but it is 12V buffered.

 

Yeah, FICM voltage hold steady at 48 +/- 0.5V, the other two are at 11.5V KOEO and 13V engine running.

I have checked the clutch connect, but I have had the same issue happen with both the old and new clutch.