Engine Shutdown While Driving

[Bill Heffernan]

Good morning. We were having a great trip in the PNW until we started our drive this morning. Our rig has repeatedly shutdown while driving. I nursed it to a Love's where we are figuring out next steps. The symptoms - loss of power, zero turbo boost, it coasts for a bit before total shutdown. When it shuts down I'm getting a low battery message (when running it showing 13. and loss of engine comms message. Any ideas? Thanks

[Fred Cook]

Are you able to start it up after it shuts down? I had a similar problem but mine would start up again but shut down periodically. My problem was the ignition relay in the rear run box went bad.

[Bill Heffernan]

Thanks Fred. Yes, we were able to re-start. We found a local mechanic. He went through all the electronics and did not find any issues. He pulled and checked fuel filters - one of them looked a bit rough he said, replaced them and checked fuel pressure, again no problems. After that it ran fine for about 20 miles, when we lost power briefly, but it did not shutdown. We kept going for anther 150 miles with no issues. At this stage it appears that it was a fuel/fuel filter issue. We are back on the road tomorrow. Hopefully no more issues.

[Scott Shearer]

Bill,

It’s unlikely that either a “low battery” message or a “loss of engine comm” message would be caused by fuel filters. A “loss of engine comm” message usually indicates that the engine ECM is not communicating with the coach systems.

If this happens again, there are a couple of things you can check to determine whether you’re dealing with an electrical issue.

First, if you have a functioning Aladdin system that displays engine/transmission data, turn the ignition key to the run position and check whether the engine/transmission page shows all zeroes for the engine data. All zeroes would indicate that the engine ECM is not transmitting engine data.

Next, open the rear run box. Again, with the ignition key in the run position, look at circuit boards #1 and #7 (they are marked PCB1 & PCB7).
On PCB7, all LEDs should be illuminated red; fuses 1, 2, and 3 provide power to the engine ECM.
On PCB1, the rear start PCB, LEDs D1, D2, D3, D5, and D8 should all be illuminated.
LED D1 should be green.
LED D2 should be yellow.
LED D3 should be red.
LED D5 should be yellow.
LED D8 should be red.
If LEDs D1, D2, and D3 are not illuminated, you do not have ignition power at the circuit board or to the engine ECM. This will defuel the engine and shut it down. Check the 5-amp fuse on PCB1 labeled IGN FUSE.

The following two conditions are probably not roadside repairs:
If LEDs D2 and D3 are illuminated but D1 is not, the ignition relay is probably bad.
If only LED D3 is illuminated, further diagnosis will likely be needed.

There are a number of possible failure points in the ignition system on this era of coach, but a common problem is the ignition circuit board in the rear run box, PCB1, or one of its components, as Fred mentioned.

EDIT***
Also, avoid hanging extra keys from the ignition key. These Monaco coaches use an older style GM ignition switch and don’t like having extra weight hanging on them.

You can use a simple fused jumper wire to temporarily bypass the entire coach ignition run circuit. This can at least get you to a safe place. After experiencing an uncommanded engine shutdown with no restart, I won’t leave home without the jumper. My shutdown was on a busy two-lane Oregon coastal road with no shoulder—was not fun.

I’ve included the following images:
PCB#1 with correct LEDs illuminated when the ignition key in the run position.
Ignition bypass jumper.
Ignition bypass connection locations.

-Scott

[Eric Maclean Co-Admin]

Scott
Your last post is very detailed and could be very helpful to anyone will similar coaches and problems on the road
Thank you for your input.

Eric