As mentioned yesterday, after the Rancho Jurupa campground we were going to head to a Thousand Trails park in the Palm Springs area, but due to Check Engine and Malfunction Indicator lights coming on, and the DEF gauge jumping to full during a drive, we decided to take the coach to a nearby Cummins service shop (the manufacturer of the diesel engine).

Here’s the Check Engine light and DEF gauge during the drive:

After filling the diesel fuel and DEF, we had both Check Engine and MIL, with two errors displayed:

(Yes, the dash is a bit dusty.)

The Cummins shop:

Another Tiffin Allegro Bus had arrived ahead of us:

Service bays:

After waiting for a few hours, they indicated that they wouldn’t have time to diagnose us that day, so we loaded up our truck with some clothes, our cat, and other supplies, and headed to a hotel:

Here’s our coach over the back of our truck:

 The next day, they still hadn’t gotten to it, so we popped by our coach to pick up some more clothes and other items:

After two nights in a hotel, they finally diagnosed it. They only found the first of the error codes, “SPN 111 FMI 18”, which related to low coolant. So they topped up the coolant and cleared out the errors.

The other error, “SPN 3031 FMI 9”, relates to the DEF system. which was more concerning. But they can’t fix something that they can’t reproduce. So we’re hoping that was either a one-off fluke, or somehow related to the other error.

We’re concerned about it as there have been fairly widespread reports of the DEF head sensors failing, and the replacement part can be hard to come by, due to the current global supply chain issues. If we needed to replace it, we could have to wait weeks. Though I’ve also heard that Tiffin can overnight the part, or that Cummins can do a software patch to bypass the error.

So far so good; as of this writing things have performed correctly. It was convenient that we were near a Cummins shop, but we just hope that we don’t have a failure while out in the boonies somewhere.