I was driving in northern Texas last Saturday and at pne point during the drive I found myself going 15 mph on the interstate as the rain was literally falling in sheets and I was completely blind beyond 5 feet in front of my vehicle. The water was never high on the ground but while I was slowly cruising along trying to follow the middle white stripes I saw a "check fuel filter" message appear. My fuel filter was changed 9k miles ago. My mileage average suddenly dropped from 40 mpg at an average of 67 mph to 35 mpg at the same speed (this was shortly after I had passed through the storm as I reset the trip indicator at that point to troubleshoot).

On my way back to San Antonio just a few hours later the message had vanished and my average mpg at 67 mph increased back to 40 again...

With all of that being said, is the engine compartment water-tight?? Has anyone else run into this before when driving through a storm?

 

The same exact thing that happened to my car! We took a road trip a week ago, and we had rain pretty much everyday we were on the road. Yesterday and today, on our way back from Denver to San Antonio, I had the check fuel filter message. Like you, I did not cross any high water. I got this car as a CPO about 2 months ago so I don't know when the fuel filter was changed. However, the car has had all it service, and according to what I read, the fuel filter is changed at 20k. There is a recall for the fuel filter, which is located in the fuel tank, that can be accessed from underneath the rear seat cushion. Considering all the rain, I hope it's something simple maybe water got in the connection. I'm also thinking the increased humidity from the rain on a daily basis may have caused more water in the fuel and that caused the sensor to trip. It's also possible there could've been a bad batch of diesel, but not likely considering I only use top tier fuels (i.e. Chevron, Shell, Exxon, etc.) I am scheduled to take it in tomorrow to see what caused the message, and I will report back with more information.

 

It appears that the location for the diesel filter is located on the engine, wedge somewhere alongside the intake manifold, and not under the rear seat as previously believed.

Attached is the information from the service invoice.

Greg

 

Thank you for the update gcssat. Did your status message remain well after it initially appeared? I wonder what triggered our warnings in the first place if no water penetrated the fuel filter and lines?

 

When I saw the message first appear, I cleared it off the screen with the "OK" button on the steering wheel. After pit stops along our trip, it did appear a couple more times. I did not notice or experience any performance issues.

Like you, I'm scratching my head to why the fault code appeared if there wasnt water present. I'm thinking there is a humidity sensor tied to the system as a redundant backup in case the actual water sensor fails. Maybe the 100% humidity for the extended period of time caused havoc on the connectors. Maybe there was water present but the heat from the engine evaporated the water. Who knows? The SA did tell me that I was due for the fuel filter change at 40k.

I found the TSB as mentioned in the service invoice:

Check TSB topic LI47.20-P-054958
Combination message: "Clean fuel filter" as well as fault code (FC) 162500, P226997 or 171600 stored in engine control unit

The diesel fuel filter has a water separator that should be drained at every oil change by unscrewing the knurled knob and letting the water out.

Combination message: "Clean fuel filter" as well as fault code (FC) 162500, P226997 or 171600 stored in engine control unit
Topic number LI47.20-P-054958
Version 3
Design group 47.20 Fuel pump, filter
Date 07-01-2013
Validity All cars with OM642 and OM651
Reason for change Reword remedy step 10

Complaint:
Combination message: "Clean fuel filter" is displayed.

The fault code 162500 (water level message - Bosch) or P226997 (water level message - Delphi) or 171600 (filter load - Bosch) is stored in the engine control unit.
Cause:
-
Remedy:
With FC 162500 or FC P226997:

1. Drain water from the fuel filter: Drain off approx. 200 ml (not possible with Q16 - the filter must be changed in this case).

2. After approx. 1 min, at least 50 ml of water must settle at the bottom of the measuring cup - in this case, the message was justified - delete the FC and return the vehicle to the customer.

3. If no water settles in the measuring cup, the message was due to incorrect detection.

4. Check the contacts at the fuel filter/glow time control unit and cable set for moisture.

5. Delete the FC and run the engine at idle for 2 min. Please observe whether the combination message is set again.

6. If the combination message does not occur, please hand the vehicle back over to the customer.

7. If the combination message is set again, please change the fuel filter.

8. Delete the FC and run the engine at idle for 2 min. Please observe whether the combination message is set again.

9. If the combination message is set again, please replace the glow time control unit.

10. If the combination message is to be set again, please create a PTSS case.

With FC 171600:

1. Measure the pressure drop at the filter using 2 pressure gauges.

2. If the pressure drop is greater than 0.7 bar, change the fuel filter.