Passed required smog but active trouble code shown: U0121

[Danny91364USA]

Nothing appears on my dashboard and this only came up when I did the smog test.

U0121

Can anyone shed some light?

Anyone else got this? Then again, unless you took it in for a smog test, you may not even know!

DK

 

[Eagle7]

It means "lost communication with the anti-lock brake system (ABS) control module" according to the OBD code list. Not sure how or why a smog test would trigger that.

 

[Danny91364USA]

It means "lost communication with the anti-lock brake system (ABS) control module" according to the OBD code list. Not sure how or why a smog test would trigger that.

It was not the test per se, it was the fact they connected the OBDI and saw it. They printed it to show me. Now I have to deal with it...

 

[Eagle7]

It was not the test per se, it was the fact they connected the OBDI and saw it. They printed it to show me. Now I have to deal with it...

I wouldn't necessarily worry about it. It just show that it happened once, not that it's a permanent condition. It could have been many things, including a glitch. I would recommend clearing it if you have an OBD2 reader, and keep an eye on it to see if it happens again. If it's a permanent situation, it will flag again right away. These new cars are more complicated than ever before, so it seems they can have momentary glitches when new as they're settling in.

 

[Smwalker]

Sounds like you might be talking about a "permanent code"

If so you do not have to do anything about it. It is not an indication that anything is wrong with your car. Just that there was something wrong at one time. The ecu is waiting for similar conditions to test for that code and if it does not see the fault again it will clear the code. Not hurting anything hanging around in there. And since you passed your smog you are set. Enjoy your car.

What state was this?

 

[cdn_alien]

Nothing appears on my dashboard and this only came up when I did the smog test.

U0121

Can anyone shed some light?

Anyone else got this? Then again, unless you took it in for a smog test, you may not even know!

DK

I've had that error code probably five or six times. After the first occurrence, I took it to the dealer and they said everything was fine and cleared it. After that, I've had it come back within a day, and sometimes it may take a few weeks. But each time, I clear it with my OBDII reader. I'm not too worried, losing comm or losing ABS is not the end of the world.

 

[AlohaRob]

I had this very thing happen to me. I bought a bluetooth type OBD2 port scanner but for some reason it won't allow me to clear this code. Can anyone recommend a really good one?

 

[Smwalker]

I had this very thing happen to me. I bought a bluetooth type OBD2 port scanner but for some reason it won't allow me to clear this code. Can anyone recommend a really good one?

If it is a permanent code no code reader can clear it. Is there a reason you need to clear it? Is your check engine light on?

What State are you in?

 

[AlohaRob]

If it is a permanent code no code reader can clear it. Is there a reason you need to clear it? Is your check engine light on?

What State are you in?

I don’t know, it seems like there isn’t a consensus as to whether it is permanent or not. It’s not a check engine light, it’s a triangle with an exclamation mark in it. I’m in Hawai’i for what it’s worth.

 

[cdn_alien]

I use a OBDLink MX+ and seems to work for me. And it is a permanent MIL light that stays on, until I clear it.