Service 4WD Message on 2021?

[Doug Ram]

Folks, I am getting the occasional "Service 4WD" message when operating in 4WD Automatic on my 2021 Ram 1500. I had thought it might have been because of uneven tire pressure but it's still coming on with all 4 tires within a pound of each other.

This seems to be a minor problem. It never comes on in any other mode, I only use Auto mode in heavy rain, and I didn't expect the truck to even have an Auto mode 4WD..... But still it is nice to have for when the wife drives it in winter.

Any ideas of what to expect when I drop it at the dealer tomorrow? Is this a sign of something really major that has to be fixed?

 

[Doug Ram]

Folks, I am getting the occasional "Service 4WD" message when operating in 4WD Automatic on my 2021 Ram 1500. I had thought it might have been because of uneven tire pressure but it's still coming on with all 4 tires within a pound of each other.

This seems to be a minor problem. It never comes on in any other mode, I only use Auto mode in heavy rain, and I didn't expect the truck to even have an Auto mode 4WD..... But still it is nice to have for when the wife drives it in winter.

Any ideas of what to expect when I drop it at the dealer tomorrow? Is this a sign of something really major that has to be fixed?

The problem appears to be related to a wiring harness for the four-wheel-drive system. Dealer says the part is on back order, now there’s a surprise, and won’t be coming in until July 18.

 

[Jim Clements]

The problem appears to be related to a wiring harness for the four-wheel-drive system. Dealer says the part is on back order, now there’s a surprise, and won’t be coming in until July 18.

Did you replace harness? Did it fix it? My light comes on temporarily with "locker" light. Only happen when trans is cold and something to a stop.

 

[Doug Ram]

The new harness fixed the problem. The message has not recurred.

Now Stelantis needs to get my dealer the part needed to do the recall for the defective high pressure diesel fuel pump.

 

[sdkeach]

Glad I found this post. I have a '21 RAM 1500. Currently 75K miles. Bear with me here. The other day I started out my drive way and got a ding ding ding and a message "Service 4wd' Then an idiot light came on. The light went out after a couple miles. during my 58 mile commute to work it did it three more times. Get off work..fire up my truck...all kinds of dings. "Service Stabilitrak" Service Trailer Brake system". then the red Stabilitrac light came on. Drove it 15 feet and the "Service 4wd" code popped up and the service 4wd light is now lit up. 4wd worked. Conditions were wet, slushy,rainy. Pulled over...rebooted truck. all good. Jump ahead two days...truck worked great entire 2 days, no codes or lights.....Day three...Rain returns.....problem returns. I am thinking an electrical connector needs to be cleaned, dried, and dielectric grease applied? I just had my Tailgate inspected for that recall. dealer wanted to charge me $157 to TS the problem even though I have an extended warranty....Sorry for the long read. thanks for hanging in here....Please share thoughts....Doug Ram....can you elaborate on your harness issue? Do you have a part number or location or any info/instruction you can share? Thanks a ton! Doug.

 

[Doug Ram]

Glad I found this post. I have a '21 RAM 1500. Currently 75K miles. Bear with me here. The other day I started out my drive way and got a ding ding ding and a message "Service 4wd' Then an idiot light came on. The light went out after a couple miles. during my 58 mile commute to work it did it three more times. Get off work..fire up my truck...all kinds of dings. "Service Stabilitrak" Service Trailer Brake system". then the red Stabilitrac light came on. Drove it 15 feet and the "Service 4wd" code popped up and the service 4wd light is now lit up. 4wd worked. Conditions were wet, slushy,rainy. Pulled over...rebooted truck. all good. Jump ahead two days...truck worked great entire 2 days, no codes or lights.....Day three...Rain returns.....problem returns. I am thinking an electrical connector needs to be cleaned, dried, and dielectric grease applied? I just had my Tailgate inspected for that recall. dealer wanted to charge me $157 to TS the problem even though I have an extended warranty....Sorry for the long read. thanks for hanging in here....Please share thoughts....Doug Ram....can you elaborate on your harness issue? Do you have a part number or location or any info/instruction you can share? Thanks a ton! Doug.

Where I live its always raining or snowing, so I am not sure that was a factor. And I did not get "service stabiltrak" message and have had no problems with the trailer brake system.

However, my EcoDiesel has the 100,000 mile diesel drive-train warranty so I took it to the dealer. All my paperwork said was that they replaced the 4WD harness after diagnosing "service 4WD" code. No part number listed.

If my dealer tired to charge me for "diagnosing" the tailgate recall, they would never ever see me again. There are plenty of dealers within a 100 mile radius of my home!

Meanwhile, I am still waiting for a new high pressure fuel pump and yesterday I got yet another recall notice. This recall concerns the trailer reverse steering control, a system that has proven to be both not very useful and quite troublesome.

While this may make it appear that the Ram isn't terribly reliable, the issues have been minor. It's now got 55,000 miles and has never broken down, failed to start or needed a major costly repair. Which is more than I can say of any of the other vehicles I've bought from GM, Toyota, Nissan and Ford since 2005, all of which needed a tow after they left me standing on the side of the road, and all were vehicles with less than 50,000 miles on their odometers.

 

[Loudram]

Glad I found this post. I have a '21 RAM 1500. Currently 75K miles. Bear with me here. The other day I started out my drive way and got a ding ding ding and a message "Service 4wd' Then an idiot light came on. The light went out after a couple miles. during my 58 mile commute to work it did it three more times. Get off work..fire up my truck...all kinds of dings. "Service Stabilitrak" Service Trailer Brake system". then the red Stabilitrac light came on. Drove it 15 feet and the "Service 4wd" code popped up and the service 4wd light is now lit up. 4wd worked. Conditions were wet, slushy,rainy. Pulled over...rebooted truck. all good. Jump ahead two days...truck worked great entire 2 days, no codes or lights.....Day three...Rain returns.....problem returns. I am thinking an electrical connector needs to be cleaned, dried, and dielectric grease applied? I just had my Tailgate inspected for that recall. dealer wanted to charge me $157 to TS the problem even though I have an extended warranty....Sorry for the long read. thanks for hanging in here....Please share thoughts....Doug Ram....can you elaborate on your harness issue? Do you have a part number or location or any info/instruction you can share? Thanks a ton! Doug.

I would agree with your initial diagnosis. Could be a moisture issue. Checking connections and adding dielectric grease is a smart idea, but I don't know which connector to check. Sorry I couldn't help you more.