"Service 4WD warning"

[WanderingTs]

I have not had any of the recent service recalls done, so hopefully that is not my problem. I was out wheeling/hunting the other day and in four low. I went through a large mud hole which had been frozen over in the morning. Now that the sun was out, it was pure mud. I had been through this particular hole many times before in prior years with no issues. This time, apparently enough mud had been thrown out by others that I found a large rock with my rock sliders. I also heard a loud bang on the passengers side (opposite where the rock was) and my "service 4WD system" warning light came on. I backed out of the hole and checked underneath. Nothing visible. Turned the Jeep off/on and the code reset. Drove forward, the warning activated again. I shifted out of 4 low, turned the engine off/on and it reset and did NOT come back on. I shifted back into 4-low and the warning came on again. Obviously this is a 4-low related issue. I came home and checked DTC codes. The only one was p 171 which appears to be an unrelated fuel system code. Where do I even start to try to figure out what is wrong? No codes, nothing appears broken, nothing abnormal other than the warning. Thoughts besides take it to the dealer?

[LeadFoot]

I'm not sure what year Jeep you have, but there is a TSB concerning service 4WD system light and the lack of a trouble code. You if it applies to your Jeep then you may want to take it in.


2616

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SUBJECT:
Flash: Erroneous Fault Warning - Service 4WD System Illuminated
OVERVIEW:
This bulletin involves selectively erasing and reprogramming the Final Drive Control
Module (FDCM) with new software.
MODELS:
2005 - 2006 (WK) Grand Cherokee
**2005** - 2006 (WH) Grand Cherokee (International Markets)
2006 (XK) Commander
2006 (XH) Commander (International Markets)
NOTE: This bulletin applies to vehicles equipped with Quadra Trac II (sales code
DHX) or Quadra Drive II (sales code AWB) **and built on or prior to May 19,
2006 (MDH 0519XX)**.
SYMPTOM/CONDITION:
The vehicle operator may describe “Service 4WD System” is illuminated but there is only a
stored Diagnostic Trouble Code (DTC) present or no fault present when the FDCM is
interrogated by a Scan Tool (StarSCAN®).
DIAGNOSIS:
Using StarSCAN® with the appropriate Diagnostic Procedures available in
TechCONNECT, verify all systems are functioning as designed. If DTCs are present
record them on the repair order and repair as necessary before proceeding further with this
bulletin.