U0021?

[Rlewis2288]

Hello new to the forum. So I was changing the lights on the back of my gauge cluster and afterwards I have a CEL. The code showing up is U0021 nothing I seem to look up is really explaining what it is. Can someone help me please or point me in the right direction. It's a 2007 Dodge Ram 1500 4x4

 

[HemiLonestar]

U0021 Low Speed CAN Comm Bus + Open
You have a bad connection on the back of your cluster most likely since that was what you last messed with. Check the connectors and how well they connect.

 

[Rlewis2288]

Thanks for the reply. Although if everything on my cluster works why would a code show up all of a sudden for that?

 

[turkeybird56]

Loose wire, ground, the choices are endless. Ground being loose usually the critter giving issues, but these are all just Internet guesses.

 

[Rlewis2288]

I just ran out to my truck and held the trip button and turned ignition on. Everything seemed to light up. Lights I didn't even know my cluster had showed up. All the needles moved as they should. So should I be real worried about this code?

 

[GTyankee]

You mentioned that you changed bulbs.
Did you just refresh all the bulbs with OEM type
or
Did you change the type of bulb with color or LED, or ...

 

[turkeybird56]

No way on an internet guessnosis could I know. U can always ignore but keep an eyeball on all. I got a 2019, and it is an electronic snafu/monster. I currently have an electronic BCM issue where I had the AC TSB done and my AC/HEAT will not initiate on remote start, till I hit the push to start. So who knows, LOL.

 

[Rlewis2288]

I switched my bulbs to some Blue LED ones. I was gonna do my entire truck interior the same. I love my truck but it seems as soon as I fix one issue another one comes up. I can't stay ahead of it to just do something fun to the thing. So I figured what's 6 dollars for some bulbs to do a little something for myself.

 

[GTyankee]

You may need to add a resistor into the line
The LEDs may not draw enough power
I don't know anything about it, but something similar has happened before with Head, Fog, & Signal Lights

Good Luck