my truck is throwing DTC code U0645 - What is this and can I fix this myself?

[MValdez]

I just got my truck back from dealership last week where they replaced a cracked exhaust manifold and cracked cylinder head. I scanned my truck and the code U0645 is coming up. From what I have found in my search this is a bad oxygen sensor. Is this true and is this a "plug-n-play" fix i can do myself?

 

[Jimmy07]

Lost communication with active air dam module. Probably from when it was disconnected when the work was done. What prompted you to scan for faults, was there a check engine light? If not, just clear the fault- that fault doesn’t request a MIL until the second consecutive trip with an actual failure of a circuit in that module.

 

[MValdez]

As soon as I drove my truck off the lot from dealership the check engine light came on and I immediately drove it back to service desk. Mechanic said my active air damn was causing the check engine light to come on so he disconnected it and they ordered me a new one. Said they would call me when part comes in. My truck actually throws 2 DTCs- U11E9 & U0645 .
Isn't the U11E9 my air damn and the U0645 oxygen sensor? My check engine light has come on twice since I got it back from dealership . it is currently off but the DTCs concern me as I am nearing the end of my warranty and I would prefer to have anything and everything fixable under the warranty completed before it becomes my responsibility and my $ to have to fix things.

 

[Jimmy07]

As soon as I drove my truck off the lot from dealership the check engine light came on and I immediately drove it back to service desk. Mechanic said my active air damn was causing the check engine light to come on so he disconnected it and they ordered me a new one. Said they would call me when part comes in. My truck actually throws 2 DTCs- U11E9 & U0645 .
Isn't the U11E9 my air damn and the U0645 oxygen sensor? My check engine light has come on twice since I got it back from dealership . it is currently off but the DTCs concern me as I am nearing the end of my warranty and I would prefer to have anything and everything fixable under the warranty completed before it becomes my responsibility and my $ to have to fix things.

Those are both communication faults, with the U11E9 being the active grill shutters. The U11E9 is specific to the LIN bus circuit for the AGS, so I would start by checking that circuit, as it is shared with the air dam module.

 

[mikeru82]

Disconnecting the active air dam does not throw a code. It's probably the active grille shutters.

 

[MValdez]

Disconnecting the active air dam does not throw a code. It's probably the active grille shutters.

yes it was the active grille shutters. that's my mistake . thank you

 

[User_110637]

As soon as I drove my truck off the lot from dealership the check engine light came on and I immediately drove it back to service desk. Mechanic said my active air damn was causing the check engine light to come on so he disconnected it and they ordered me a new one. Said they would call me when part comes in. My truck actually throws 2 DTCs- U11E9 & U0645 .
Isn't the U11E9 my air damn and the U0645 oxygen sensor? My check engine light has come on twice since I got it back from dealership . it is currently off but the DTCs concern me as I am nearing the end of my warranty and I would prefer to have anything and everything fixable under the warranty completed before it becomes my responsibility and my $ to have to fix things.

Hi,
I have 11e9 and u0645. What did you do for a fix? Your help would be appreciated.
Ray

 

[theblet]

Try disconnecting your AAD. Mine threw an AGS code, but it’s actually the AAD. They are both on the same circuit.

 

[mikeru82]

Hi,
I have 11e9 and u0645. What did you do for a fix? Your help would be appreciated.
Ray

It's helpful if you post the details of your truck when asking for help with an issue. It seems that people with '22 models have seen trouble codes when they unplug their AAD, where '19 thru '21 models don't seem to do that.

 

[theblet]

It's helpful if you post the details of your truck when asking for help with an issue. It seems that people with '22 models have seen trouble codes when they unplug their AAD, where '19 thru '21 models don't seem to do that.

I didn’t know that changed.

 

[mikeru82]

I didn’t know that changed.

I added that as a disclaimer. No personal experience with that, but I read a few posts in a related thread where '22 owners claimed they get a CEL when they unplugged their AAD.

 

[User_110637]

Hi,
I have 11e9 and u0645. What did you do for a fix? Your help would be appreciated.
Ray

It is a all new 2019 Ram , 5.7 hemi. I disconnected the lower bumper air dam and service engine light does not return and the grill shutters work now. Does that mean replacing the lower air dam will be the fix?

 

[theblet]

It is an all new 2019 Ram , 5.7 hemi. I disconnected the lower bumper air dam and service engine light does not return and the grill shutters work now. Does that mean replacing the lower air dam will be the fix?

More than likely, yes. Most people just ditch it since it doesn’t really help anyway. Might save 1/2 a mpg at 60mph+ if that.

I actually had someone follow me in my truck so I could see if it was deploying, and it was not. It deploys around ~30mph.

 

[mikeru82]

It's likely that would fix your problem. I'm pretty sure there's a service bulletin about this, and extended warranty coverage for some 2019 models. There are other threads on this, and at least one of those has the TSB number. But the easiest thing to do is unplug or just remove it entirely. I never noticed any real difference in fuel economy after removing them.

 

[theblet]

It's likely that would fix your problem. I'm pretty sure there's a service bulletin about this, and extended warranty coverage for some 2019 models. There are other threads on this, and at least one of those has the TSB number. But the easiest thing to do is unplug or just remove it entirely. I never noticed any real difference in fuel economy after removing them.

That's true, there is a recall for the AAD. I completely forgot about that. So if you really want it fixed it shouldn't cost anything.

 

[mikeru82]

That's true, there is a recall for the AAD. I completely forgot about that. So if you really want it fixed it shouldn't cost anything.

If I had more time I'd search for it. Shouldn't be too difficult to find if someone has some time.

 

[theblet]

Active Air Dam Warranty Letter from FCS

 

[SaltyAzGrunt]

I have the same issue due to installing an offroad bumper. If you get any updates can you let me know?

 

[MValdez]

Hi,
I have 11e9 and u0645. What did you do for a fix? Your help would be appreciated.
Ray

both codes are related to an issue with the active air dam. when i had my truck serviced , replacing a cracked cylinder head, they disconnected the active air damn and must have damaged it because they had to order me a new one and it took 6 months for it to come in from back order. for those 6 month i was unable to use the "remote start feature" because when the active air damn is disconnected the truck throws codes 11e9 and u0645. once the new AAD was installed the issue was fixed. I've had so many problems with this truck from the first 100 miles - 50K miles. If the market wasn't as ridiculous as it is right now I would have ditched my 2019 Dodge "Sheep" months ago.

 

[Charon]

Any chance you know where they disconnected it?
I had leaky exhaust manifolds replaced at the dealer now I have the same issue.
I'm going on a long distance trip that could knock me out of warranty mileage...