lack loss of, no power on hills engine sluggish
Limp Home Mode (LHM) Possible Causes
Limp Home Mode or Limp-in is an operating condition set by the Sprinter computer(s). Technicians may refer to the vehicle computer as the ECU Engine Control Unit, ECM engine control module, or PCM power-train control module. The ECM or TCM transmission control module both have the capability of setting a LHM state. LHM limp home mode is a programmed response for the computer recognizing abnormal operation of your engine/drive-train. The intent is that it limits the power available and therefore will allow you to operate the engine and keep driving, but limit any damage to your engine and drive train.
There are various levels of LHM possible. The most severe is the transmission limited to one forward gear (usually 2nd gear) and reverse, with engine power reduced. LHM is not really a symptom as such, it is more a normal pre-programmed response to the recognized problem. The MIL Malfunction Indicator Light, or sometimes called the CEL Check Engine Light may or may not be lit when the computer calls for LHM.
Please read this: It is important to note that all loss of power situations are not necessarily LHM set by the computer. Regular old problems like a plugged fuel filter, dirty air filter, mechanical turbo control linkage failures, plugged exhaust system, etc. may also cause a lack of power which is not computer set/related. The computer only sets LHM if it becomes aware of a problem, sometimes the sensors don't notice so it just doesn't know. It would be so much easier if MB included a "LHM Set" dash light indicator.
Any diagnosing of why your Sprinter went into LHM needs to include reading the trouble codes available. It very well may require using a dealer computer scan tool. That is a DRBIII or DAD for T1N model NAFTA Sprinters (2006 and older).
Added:
No Scan Tool??? Maybe this will work.
Thanks goes to Nick.
We don't know what the 7 times key sequence really does. It likely erases all DTC history. That can be a very bad thing if you are under warranty.
Although this LHM info is posted in a T1N section much of it applies to both the T1N and NCV3. Please note that the model specific information is intermixed.
20120103 edit:
My personal method of determining whether there is a computer set LHM.
Sometimes the computer isn't involved with low power situations. The test I feel applies is this:
Lower forms of LHM.
After having not made any repairs or alterations, if your normal operation and power returns after a simple shutdown and restart then whether you have an MIL (aka CEL) lit or not, the computer was involved in limiting the power. In most cases the symptoms will eventually return.
Additional info:
More severe forms of LHM.
If a shutdown/restart doesn't return operation to normal and you have a MIL (aka CEL) lit then the computer has likely set an LHM which requires repairs and may require clearing the codes with a scan tool.
Limited to one forward gear (likely 2nd) and reverse gear.
The most severe level of LHM. This form of LHM is often related to transmission problems. This requires repairs and most always requires reset by a scan tool capable of communication with the Transmission Control Module TCM to restore proper operation.
These are some known conditions that may cause the ECM to set LHM.
Turbo Boost Pressures abnormal
Any time the turbo boost, or the Mass Air calculated value, is not in a range that the ECU considers normal it may set LHM. Some possible turbo boost leak areas are:
In 2004 - 2006 NAFTA Models - Turbo resonator failure. Typically a seam cracks. One indication of leakage is oil being found on that cracked seam.
In all models - splits in the turbo outlet hoses and loose clamps are a possibility. Cracked Charge Air Coolers have been reported. Charge Air Cooler cracks don't seem to be a common failure, but should be inspected. There is a mechanical turbo blade positioner on pre-2004 OM612 engines and an electrical positioner on the 2004 - 2006 OM647 engines. Anything that may allow turbo air to leak, or anything that reduces turbo air flow to the manifold can be a problem.
Turbo boost system leaks should be repaired in a timely manner. The turbo may be set to full output to try and supply proper intake pressures if there is a leak. Operating at full output all the time may reduce the service life of the turbo.
EGR Exhaust Gas Recirculating Problems
The EGR has been known to cause an LHM response. On pre-2004 OM612 engines an EGR cleaning may address the problem. Post 2003 model EGR units do not seem to need regular cleaning. There is recent threads that indicate post OM612 EGR valves will respond to DIY cleaning if it is discovered that the valve doesn't snap back closed freely. DO NOT REMOVE THE EGR body SECURITY SCREWS WITH THE LITTLE REJECTION NUB IN THE TORX HEAD.
After I wrote the above introduction rather than re-inventing the wheel I contacted JD Caples to see if he had any input. The following is what he contributed. Many thanks to Jon for his efforts and input. I just cut and pasted, so it may be a bit disjointed. Additional LHM cause information posted by others is encouraged. Hope this does some good. vic
Jon's Input:
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 (Diagnostic Trouble Codes) 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. 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
Limp Home Mode (LHM) Possible Causes
Limp Home Mode or Limp-in is an operating condition set by the Sprinter computer(s). Technicians may refer to the vehicle computer as the ECU Engine Control Unit, ECM engine control module, or PCM power-train control module. The ECM or TCM transmission control module both have the capability of setting a LHM state. LHM limp home mode is a programmed response for the computer recognizing abnormal operation of your engine/drive-train. The intent is that it limits the power available and therefore will allow you to operate the engine and keep driving, but limit any damage to your engine and drive train.
There are various levels of LHM possible. The most severe is the transmission limited to one forward gear (usually 2nd gear) and reverse, with engine power reduced. LHM is not really a symptom as such, it is more a normal pre-programmed response to the recognized problem. The MIL Malfunction Indicator Light, or sometimes called the CEL Check Engine Light may or may not be lit when the computer calls for LHM.
Please read this: It is important to note that all loss of power situations are not necessarily LHM set by the computer. Regular old problems like a plugged fuel filter, dirty air filter, mechanical turbo control linkage failures, plugged exhaust system, etc. may also cause a lack of power which is not computer set/related. The computer only sets LHM if it becomes aware of a problem, sometimes the sensors don't notice so it just doesn't know. It would be so much easier if MB included a "LHM Set" dash light indicator.
Any diagnosing of why your Sprinter went into LHM needs to include reading the trouble codes available. It very well may require using a dealer computer scan tool. That is a DRBIII or DAD for T1N model NAFTA Sprinters (2006 and older).
Added:
As a point of clarification.
No scan tool can "Clear LHM's".
Limp Home Mode LHM is a reduced power mode enabled to protect the drive train from severe damage. It is set by a module(s) when certain unusual vehicle operating conditions are detected.
LHM response can range from simply disabling the turbo (reduced power) to setting engine RPM limits to limiting the transmission operation. The transmission operation can be limited to Park/2nd gear/neutral/reverse, and in the most severe lockout, no transmission drive response at all.
Repairs or other corrections to the vehicle need to be effected to restore operation. Most all lower level engine related LHM modes will be disabled without clearing the DTC's aka codes once the offending problem is corrected, or if the detected problem just goes away (for a time).
Transmission LHM
Even after repairs, to restore proper operation transmission related LHM generally does require accessing the TCM to clear the transmission related DTC's. A Sprinter specific scan tool aka "higher level" is needed to access the TCM to clear those DTC's. Clearing the companion DTC's found in the ECM aka ECU is not enough.
There is a danger in not fully recording the DTC's before clearing a module history. DTC's can be cleared which may never again present to help aid in troubleshooting. A failing part can trigger a DTC and then not be noticed after that failure.
Loss of history using a generic OBDII scan tool can be even more devastating to troubleshooting. A generic tool has the ability to clear codes which it can't even display.
If under warranty I would never clear ANY DTC history. The dealership often needs that information to apply warranty repairs. That can include mandated emissions control related extended warranty.
The act of clearing DTC's with a scan tool of itself is not a repair. Not all lack of power situations are computer set LHM.
vic
No Scan Tool??? Maybe this will work.
Thanks goes to Nick.
One caution on the above.Thought this might be useful if people are stuck in limp mode in the middle of nowhere and have no code reader. Couldn`t find the info on google when I searched so I asked my local hire van place to write it down as I forgot the sequence when they told me several months ago.
I know this works on older Ncv3`s, Ive just tried on my 02 T1N it works on that (my T1N has no central locking so I just ignored that step)
1.Key in
2.Turn ignition on and off 7 times (do not start)
3.Take key out and lock with remote button on key
4.Wait for lights to go out
5.Unlock with remote button on key and start .
Just tried it on my T1N and its cleared my traction control light that was stuck on, I didn`t have any lights(step 4) on to go out but it beeped when I removed the key.
Used it on a Ncv3 hire van that went into limp mode and it got me home
We don't know what the 7 times key sequence really does. It likely erases all DTC history. That can be a very bad thing if you are under warranty.
Although this LHM info is posted in a T1N section much of it applies to both the T1N and NCV3. Please note that the model specific information is intermixed.
20120103 edit:
My personal method of determining whether there is a computer set LHM.
Sometimes the computer isn't involved with low power situations. The test I feel applies is this:
Lower forms of LHM.
After having not made any repairs or alterations, if your normal operation and power returns after a simple shutdown and restart then whether you have an MIL (aka CEL) lit or not, the computer was involved in limiting the power. In most cases the symptoms will eventually return.
Additional info:
More severe forms of LHM.
If a shutdown/restart doesn't return operation to normal and you have a MIL (aka CEL) lit then the computer has likely set an LHM which requires repairs and may require clearing the codes with a scan tool.
Limited to one forward gear (likely 2nd) and reverse gear.
The most severe level of LHM. This form of LHM is often related to transmission problems. This requires repairs and most always requires reset by a scan tool capable of communication with the Transmission Control Module TCM to restore proper operation.
These are some known conditions that may cause the ECM to set LHM.
Turbo Boost Pressures abnormal
Any time the turbo boost, or the Mass Air calculated value, is not in a range that the ECU considers normal it may set LHM. Some possible turbo boost leak areas are:
In 2004 - 2006 NAFTA Models - Turbo resonator failure. Typically a seam cracks. One indication of leakage is oil being found on that cracked seam.
In all models - splits in the turbo outlet hoses and loose clamps are a possibility. Cracked Charge Air Coolers have been reported. Charge Air Cooler cracks don't seem to be a common failure, but should be inspected. There is a mechanical turbo blade positioner on pre-2004 OM612 engines and an electrical positioner on the 2004 - 2006 OM647 engines. Anything that may allow turbo air to leak, or anything that reduces turbo air flow to the manifold can be a problem.
Turbo boost system leaks should be repaired in a timely manner. The turbo may be set to full output to try and supply proper intake pressures if there is a leak. Operating at full output all the time may reduce the service life of the turbo.
EGR Exhaust Gas Recirculating Problems
The EGR has been known to cause an LHM response. On pre-2004 OM612 engines an EGR cleaning may address the problem. Post 2003 model EGR units do not seem to need regular cleaning. There is recent threads that indicate post OM612 EGR valves will respond to DIY cleaning if it is discovered that the valve doesn't snap back closed freely. DO NOT REMOVE THE EGR body SECURITY SCREWS WITH THE LITTLE REJECTION NUB IN THE TORX HEAD.
After I wrote the above introduction rather than re-inventing the wheel I contacted JD Caples to see if he had any input. The following is what he contributed. Many thanks to Jon for his efforts and input. I just cut and pasted, so it may be a bit disjointed. Additional LHM cause information posted by others is encouraged. Hope this does some good. vic
Jon's Input:
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 (Diagnostic Trouble Codes) 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. 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
Last edited:
) the problem disappeared. I'm guessing it was the engine swtiching into this LHM mode when not enough fuel was available.
I'd tried "save page", but didn't see "save page as .txt"