I'm hoping someone here might be able to offer some help as these coaches seem very common among racers.

The coach is a 36' 2004 Safari by Monaco similar to a Monaco Diplomat built on the Roadmaster RR4S Chassis with 370 HP Cummins ISL engine.

The speedometer, oil pressure and temp gauges are not working on the dash. The scan tool shows that indeed the engine is fine but the ECM is not communicating with the instrument cluster for some reason.

The original owner said the gauges stopped working after Freightliner upgraded the ECM during maintenance.

Long Story but an RV dealer has spent 18 hours troubleshooting on the original owners dime but I'm concerned its out of their league and worry they are taking advantage of the original owner. The dealer tested the gauges themselves and they are working. They also ran a makeshift harness to the dash because they thought it was the wiring harness itself.

I intend to put a https://bluefire-llc.com/website/en/motorhomes with a tablet to monitor for now now but would like to eventually figure this out.

Even while RV shopping a couple of other coaches had the same issues so it seems pretty common. Just hoping some clever racers have figured out fixes to try.

Thank You!!!

This message has been edited. Last edited by: 69dart,

Question. You stated Upgraded/Updated ECM. In cases where as the ECM was physically replaced. The ECM's come blank. The ECM's have to be what they call flashed with a ROM file and perimeters set. I am wondering if it was a bad flash/Rom.. Not uncommon where an update needs an update. JMO
But it gets into money. We are talking Strictly Freightliner here. Not the RV dealer.. Do you know what the original update/corrections were for? I know it's a long shot.

This message has been edited. Last edited by: TD3550,

had this happen to my tiffin which is the same freightliner/cummins set up. after a lot of wire tracing etc,ended up being the light bar above the gauges. the wait to start light circuit in that board had shorted. found a used part from visonrv.com

I dont think the ECM was replaced just flashed with an update during routine maintenance. The original owner doesnt seem very technical and I think he went along with whatever the shops recommended.

That sounds reasonable the update may have needed another rev or parameter update.

Or a short in the message center makes sense.

The serial bus design seems flawed because if anything shorts or hiccups along the way the gauges are lost. Silly.

This message has been edited. Last edited by: 69dart,

My Monaco oil and temp and fuel stopped working. Same deal, they couldn’t fix it. I installed new sensors, ran wires, and a new set of mechanical gauges for oil & temp. I can go 6-700mi on a tank so I just keep it full. Speedometer has always worked.

Try here https://www.irv2.com/forums/f115/
Great site.

Take a look at the silverleaf set up.
I put one in my Alpine Coach and it plugs into a port under dash for oe diagnostic hook up.
gives me all the info from the Cummins ecm.
Only thing it dosent have is fuel level.