Whenever THE RAIN come, all signal lights simultaneously ON ?

Some trucks have issues when it rains. They're very hard to find and will bankrupt you.

Do you own the truck or is it a company truck with a logging device. Anything plugged in to the ecm tends to wreak havoc with the ecm eventually.

The truck I'm driving now has a few electrical quirks from the peoplenet box that got pulled out last month.

 

You most likely have an intermittent electrical short in the ABS harness on the chassis. A wire can be rubbed thru with copper exposed at a metal contact point. When in rains the moisture makes the shorted connection and turns the fault active.

Find a good electrical shop and let them know the exact situation. Best to take it in when it’s broken.

 

Sometimes my abs light comes on when it rains. Don’t have traction control (thank god), so I can’t say anything about that.

My shop is too stupid to figure it out so I just roll with it. Seems all they ever want to do is just clear the code then tell you it’s fixed.

 

Are you in a Freightliner? Mine allowed water through the 3 clearance lights above the windshield. The fuse panel even had a factory-installed "umbrella" to protect from the expected water leak.

 

I've seen KW and Pete have the same issue, though not as common as FL's SAM Chassis failures.

His dash looks KW, so i'd start at the firewall. Check for water intrusion and all relays

 

My Volvo does it almost every time it snows or in really heavy rains while sitting. I'm fairly certain it's in the bundled harness that's laying inside the frame, I just haven't taken the time to unwrap everything and look for the damage. It tends to go away when it dries out, and the dealer charged me $400 to tell me they can't find anything wrong with it. I think most shops would prefer to just replace the harness than try and find and fix the wire, so it's probably not going to be an inexpensive fix.

 

2 issues at play, sensors work in mili volts but are in a multiplex system where the wiring is the thinnest/cheapest the bean counters can get that still allows the truck to start and drive off the lot.

Trucks are always out in the elements where UV and more can attack the wiring, after all it isn't all that good in the first place..

Anything that causes a momentary power drop can screw with the sensors in the system from moisture corrosion, etc..

Wife's car had an issue with the low oil pressure shutdown warning and chime which would suddenly come on while full of oil and running fine.

Pull over and shut it off and re-start [resets the computer] and it was fine.

Never found it, traded it away.