I replaced the head on a 2012 gmc 5.3 vortec. Now getting codes of 3401,3425,3443 & 3449. Being told it is always necessary to replace VLOM when doing this kind of work. Is that true?
Welcome to Motor Vehicle Maintenance & Repair! All of those codes are definitely related to cylinder deactivation control. I've never heard of needing to replace the VLOM during cylinder head replacement (but I don't know for sure one way or the other) ... doesn't seem quite right you'd need to. I'd replace it ... that and the lifters with HL128's and thread/plug the oil holes and get rid of the DoD ... but that's just me. What a PITB.– Pᴀᴜʟsᴛᴇʀ2 ♦Dec 13, 2019 at 13:55
Have you checked the connector is in position? Getting codes on all the channels implies a common cause. Other possibilities might be that the oil supply is insufficient - maybe the debris filter is clogged. I wouldn't think that replacing the VLOM would be necessary unless any of the solenoids have failed.– Phil GDec 13, 2019 at 14:56