Driving from the west coast to Chicago recently the yellow Check Engine light on the dash lit up, never a good feeling, especially when on a long trip in the winter. Consulting the manual, the options presented included:
1. The exhaust gas aftertreatment is malfunctioning...
2. You have used up all the fuel in the tank...
3. The injection control is malfunctioning...
None are good options, especially when the descriptions include "the engine is running in emergency mode" and "only be started another 16 times." The engine was running fine, thus options 2 & 3 didn't seem applicable, thus option 1 seemed to be the most likely candidate.
I haven't used the Blue Driver code reader (see page 20 of this thread, post 191) for quite a while (no need) so I had to re-load the ap to get it to work (new phone since the last use). Once all was working here are the Confirmed Trouble Codes I was presented with:
One of the nice things about the Blue Driver is that it gives a bit more information than just the codes, looking deeper here is what I found:
This convinced me I was dealing with a DEF issue, most likely something that would not leave us stranded on the side of I-80 in the next couple of days. So we continued on. I called the MB dealer in Chicago and read them the codes and made an appointment for the day after our anticipated arrival.
The MB dealer's diagnosis was that the DEF pump had gone out, something that parts were available for on a next-day basis AND that would be covered under the warranty extension that came with the DEF system recall. The repairs were made, the Check Engine light is gone, and all appears to be as it should be.
Going back to the Blue Driver, here is what a post-repair code search reveals:
Having a code reader on-board adds to my comfort level as I want to have as much information as possible when diagnosing a problem on the side of the road. Incidentally, Flint had a bit over 81k on the odometer when this occurred, and it is the first DEF related issue we have experienced. Talking with the dealer service rep I was told to NEVER let the DEF tank get below half full and that best practice is to fill the DEF tank every 2-3 fill ups. Seems like good advice to me.