...
The manual says to clear it using DRB3 tool. Would this make a difference?
It may very well need a DRBIII or DAD to get back to normal even if you cured the problem. I know OBDII resets don't do it all on a Sprinter.
The text below is part way through post #1. The bold about dealer reset is mine.
LHM limp home mode possible causes
https://sprinter-source.com/forums/showthread.php?t=7173
Transmission Sensor Readings (whether an actual physical condition or faulty sensor reading)
From Andy Bittenbinder:
Limp home mode is typically triggered by overspeed indications from
the internal transmission input speed sensors, engine overspeed or
improper gear ratio faults. You will likely find TCM DTCs related to
these faults. Cause can be electrical, control unit or transmission
related. Doktor A
More from Andy Bittenbinder:
The TCM(transmission control module) is able to signal the illumination of
a MIL(malfunction indicator lamp)which we see in the instrument
cluster as the small engine/trans(drivetrain) pictogragh. It does this
by communicating with the ECU(engine control unit) to trigger that
lamp. The TCM stores its own failure codes(DTCs) which can then be
accessed by technicians. It can recognize many misc. elect. problems
and some hydraulic problems.
First a few words regarding limp-home/shut down modes. Some (minor)
DTCs(failure codes) will allow the trans to resume business as usual
when problems go away on their own. More serious anomalies will shut
down all the internal solenoids and default to whatever gear you
happen to be in at the time. After you cycle the ign. key (or shift
into park) it will then go into a limp-home mode which is (usually)
2nd gear and reverse and a shut off of the TCC(torque converter
clutch). Typically a max. of about 3 cycles of the key will allow a
"temporary reset" to quasi-normal operation and
after that, limp-home
will be permanent until the dealer clears the codes. (
Bold here is mine. vic)Some failures
will not shut down all internal control solenoids. If internal
slippage is detected it may default to 3rd gear operation(in
limp-home). The transmission can even become totally disabled by
defaulting to neutral(!). Engine overrev could trigger that mode.
How does the TCM know when fluid levels are low? Or more
importantly, low enough to cause possible damage? The TCM monitors the
speed of the 2 internal drive elements. It also monitors output
shaft speed(I seem to recall it has no dedicated sensor for this
funtion but uses ABS or some other external signal). Anyway, by
monitoring these rotational speeds it can recognize (and calculate)
SLIPPAGE. In 2nd, 3rd, and 4th, for instance, the elements should be
spinning at same speeds. It probably will recognize it before you can
and then trigger the MIL and limp-home. Permanent damage then depends
on how far you drive under these conditions. Moral of the story-If
driving and engine-trans MIL lights and limp symptoms appear-STOP and
at least look inside/underneath for signs of the obvious-such as
leakage. Carry a trans dipstick and extra fluid if you're prone to
driving far from civilization. Oh, and a postscript-just to complicate
things- not all limp-homes of 2nd gear and reverse involve
transmission anomalies! For instance a failure of communication
between control units (via the CAN bus) will trigger that same
limp-home. If the TCM can't talk to the ABS control unit your going
home in 2nd gear(that is-after those 3 ign. key cycles). Andy
*****
Good luck. vic