3.0 Cold Engine Knock

[yousaveone]

I went to take the truck in for the DEF recall which apparently activates the DEF system that was previously not functioning? Where was my DEF going? I started the truck and it had an engine knock. The knock stopped after it warmed up. The dealer told me to ignore it until it throws a code. Anybody else have a cold engine knock?

[Sierra 3.0]

My engine makes a more pronounced diesel noise occasionally.  I especially noticed it after removing a heavy trailer and the first few miles unloaded it makes more noise.  I would not call it knocking though.

[yousaveone]

Can you hear it with the windows up and doors closed?

[TweetybyrdRT]

What is the DEF recall you mentioned?  I just checked mine and I haven't seen anything  2020 3.0

[BurnsMax]

It's a new recall and doesn't show under the chevy site yet.  Mine is in for warranty work and I won't get it back until next week.  They are doing the DEF recall.  I think it's just a computer flash to adjust the amount of DEF that the system uses

[yousaveone]

The recall was completed and said DEF system was deactivated and the flash reactivated it.

[TweetybyrdRT]

Thanks, probably come around on my next oil change

[ILSilverado]

I had the DEF recall done about 2 weeks ago as well. Mine was certainly using DEF fluid so im not completely sure what the re flash fixed. On the knocking I do notice at times a pronounced "big rig" sound coming from my little 6 banger that surprises me, however I think diesels just do that. Mine will do this once in a while too.

Edited July 6, 2020 by ILSilverado

[BurnsMax]

3 minutes ago, ILSilverado said:

1. I had the DEF recall done about 2 weeks ago as well. Mine was certainly using DEF fluid so im not completely sure what the re flash fixed. On the knocking I do notice at times a pronounced "big rig" sound coming from my little 6 banger that surprises me, however I think diesels just do that. Mine will do this once in a while too.

When you get the "big rig" sound it is your truck going through DPF regen.  That's the only time I get the more pronounced diesel sound.

[ILSilverado]

21 hours ago, BurnsMax said:

When you get the "big rig" sound it is your truck going through DPF regen.  That's the only time I get the more pronounced diesel sound.

It could be, because the DEF regeneration raises the idle somewhat. Sometimes I do hear a pronounced clacking sound when driving. It could also be the fuel I normally use Shell.

Edited July 7, 2020 by ILSilverado

[yousaveone]

It does it first thing in the morning, for a few miles. Starts quiet, 1 minute later a subtle knock or very loud diesel noise. Warms up a bit and the noise goes away. Noise increases with RPM and is not dependent on gear. 

[ILSilverado]

On 7/2/2020 at 11:17 AM, TweetybyrdRT said:

What is the DEF recall you mentioned?  I just checked mine and I haven't seen anything  2020 3.0

I have noticed after the reflash for the DEF TSB im using more DEF now. So keep an eye on your DEF gauge.

[TweetybyrdRT]

16 minutes ago, ILSilverado said:

I have noticed after the reflash for the DEF TSB im using more DEF now. So keep an eye on your DEF gauge.

I checked yesterday on the GM site,  no recalls coming up for my truck at all.  I might get lucky on this one.

[steve841]

Just now, TweetybyrdRT said:

I checked yesterday on the GM site,  no recalls coming up for my truck at all.  I might get lucky on this one.

It's not a recall, it's an update.  Kind of a service recall.  If you call and give them your VIN, they'll tell you if you need it.

[ILSilverado]

8 minutes ago, TweetybyrdRT said:

I checked yesterday on the GM site,  no recalls coming up for my truck at all.  I might get lucky on this one.

Mine didn't come up on the GM site either. Call your service department and have the service writer check for it.