[Mad-Max]

BLUF: does limp mode...in my case as applicable to a 2002 Dodge Dakota...affect any other components besides the transmission? IOW, does limp mode affect the engine's operational capability or performance at all?

I'm just trying to fully determine exactly what actually happens during limp mode. IIUC, limp mode means...because of sensor/computer input(s)...the transmission sabotages itself to prevent normal operation - giving the driver just enough 'capability' to get to the nearest repair shop, etc.

Last year I messed with disabling the lockup and cut the wire b/t the PCM and 8-pin plug the truck went into limp mode...but I did not notice any engine performance limitations - it all seemed to be in the tranny.

Would appreciate any thoughts.

 

[RXT]

From what I understand, "Limp home mode" is a failsafe program thats in the PCM and is intended to prevent damage to either the engine or transmission if it's operate outside of it's preset perimeters. I know that in many other vehicles including big rig engines, when "Limp home mode" is activated, engine power is derated by the PCM. For example, say the oil level drops significantly and a sensor picks this up, or the engine overheats. The computer may derate engine power and reduce engine rpms, but the engine will still be allowed to run, theoretically to allow you to get someplace safe or where you can initiate repairs. If the limp home mode was activated in a transmission, the PCM may not allow the trans to shift into certain gears or go into LU or OD, to help prevent damage to the transmission. It might also derate power to the engine, to protect the transmission. As for the Dakota, If there is a limp home mode available in the transmission, there is probably one for the engine. The FSM would show this feature.

Ed

 

[Frankg]

Have u gotten out of limp mode if so, how did u do it

 

[Mad-Max]

...I haven't figured out a way to 'prevent' limp mode, but in my case I'm replacing all of the driveline with an entire stand-alone hardware and electronics including the PCM, so there won't be any limp mode affects to my truck any more.

 

[Frankg]

Keep me up to date on that, because I'm really thinking of selling this dam dodge.I don't want too but I can't keep driving like this

 

[Mad-Max]

well...what I'm doing is no where near an 'OEM' solution - mine is pure custom fabrication. If your truck is stuck in limp mode then there's got to be a reason, and there should be some codes or something to suggest what the issue(s) might be...?

 

[Frankg]

Ok I borrowed my friend scanner an it read p0888 an po700 something about a shorted or open circuit within transmission control, tcm power relay sense circuit...So is it a bad wire?

 

[Frankg]

Yeah when this started it had read po920,po960,0999

 

[Mad-Max]

my guess is it's a bad sensor...but I'm no help diagnosing which one I'm afraid. I'd suggest searching the forums for those codes and/or talking with a couple trans shops with a good reputation and that will work with you to try to figure our the issue. I can almost guarantee someone else on this site has reported those same codes and developed a solution - just gotta search through the threads.

...the joys of owning/driving older cars...

 

[Blue069]

...I haven't figured out a way to 'prevent' limp mode, but in my case I'm replacing all of the driveline with an entire stand-alone hardware and electronics including the PCM, so there won't be any limp mode affects to my truck any more.

 

[Mad-Max]

...was there a question...?