Engine/Transmission (1998.5 - 2002) 121 code engine position sensor

[DHeasley]

truck lost power at 10,000 ft in Rockies towing 8,000 lbs off road low speed blew white smoke and missing. shut off and restarted and run fine. Truck set all week (hunting) started home low speed in town truck died restarted itself run fine all the way to Texas with normal power Shows 121 code any ideas? also where is sensor located? 02 ho 6 speed ez/rv injs. Thanks

 

[RAJohnson]

truck lost power at 10,000 ft in Rockies towing 8,000 lbs off road low speed blew white smoke and missing. shut off and restarted and run fine. Truck set all week (hunting) started home low speed in town truck died restarted itself run fine all the way to Texas with normal power Shows 121 code any ideas? also where is sensor located? 02 ho 6 speed ez/rv injs. Thanks

Mark this link: http://www.dodgedieseldatabase.com/odbii.htm



Here is what it says about the 121 code:



P0121 (M) TPS Voltage Does Not Agree With

MAP

TPS signal does not correlate to MAP sensor signal.



P0121 (M) Accelerator Position Sensor (APPS)

Signal Voltage Too Low

APPS voltage input below the minimum acceptable

voltage





Try this link for location of components

http://dodgeram.org/tech/dsl/mt_2_feb98/fuel_sys_comp.htm



Do this link to reset the APPS: http://www.dieseltrans.com/phpBB/viewtopic.php?t=614



I do not think you will have a TPS with your 6-speed, correct me if I am wrong but I think there only found on Auto's

 

[DHeasley]

RA-Thanks for reply-I have reset my apps several times (dead pedal) in the past with good results. I still have an occasional dead pedal at low rpms (1000-1500) . I also broke and cleaned all electrical plugs which helped the dead pedal occurences. I was thinking the apps needed to be replaced but wanted other opinions before I spent the money. I replace the lift pump (old pump had good pressure at 110,000 miles) as a precaution. I also had the 216 code prior to cleaning the electrical connections. However it has not reoccurred since and the truck runs strong even under heavy tow (dozer and trailer) Truck has 140,000 miles now. Any body else have any ideas?-Thanks

 

[RAJohnson]

D when you reset your APPS B4 did you do it like the method described in my last post. Or did you do it by the pedal method. If you have not done it by the voltage method in that link. I would at least do it, to make sure its not your APPS or find out how far out of spec your APPS is.



I have never drawn a 216 code, but if I ever do i will get a new HRVP and have it setting by so when it goes I will have little down time. You might be losing your VP44 slooooowly. I think the apps reset is forth a try thou. How many miles and dead pedal's have you had since the dreaded 216 code.

 

[DHeasley]

Ra-reset by the pedal method-I will try the volt meter method. Prior to resetting I had periods of completely dead pedal would not accelerate in any gear thus my concern with the apps. I currently have the dead pedal (motor wont accelerate however does not miss or return to idle ) till I downshift once or twice a month at 1,000 to 1,500 rpm in higher gears. I have 20,000 miles since 216 code. Motor starts, idles, and pulls hard even when heavily loaded other than problems mentioned.

 

[RAJohnson]

Sure sounds like you have lost your VP44. :{



But at least you got a lot more milage out of it than most people do.



Do you have a fuel pressure gauge, if not you might want to put one in. The loss of fuel pressure is the worst thing yo can do to your VP44. I know you just replaced your stock LP, but you did not say weather it was your first one or maybe the second or third?

 

[DHeasley]

The lift pump was orginal. It had normal pressure when I replaced it and the replacement has normal pressure now. I also have concerns injector pumps are being replaced when perhaps poor electrical connections were at fault. I know of a couple of local folks with the 216 code who replaced their vp and later discovered the wiring to be the problem. The local injector shops will always replace the pump with the 216 code showing without checking fruther unless the problem is not corrected. Perhaps mine is going south however I tow 26-27k with good power other than the infrequent problems mentioned. I am however aware of the injector pump problems on the 24v.

 

[RAJohnson]

D don't get me wrong, I am not trying to insult your intelligence. But I have a local friend who lost his lift pump quite some time ago, (not sure how long he ran with out it) he replaced it and every thing is still running fine except for a few dead pedal situations, and he has never pulled a 216 code. I have told him he has more than likely damaged the VP put he will not believe me until it drops dead and leaves him stranded, because it is still running. Except for a few bugs.



Good luck and let me know how this works out for you.

 

[DHeasley]

RA-Thanks for your time, input and links. I will try the pedal reset with a volt meter. If that does not help. I will start looking at the pump as I am also concerned about being left on the road. I may try to ohm out some of the wiring.

 

[JPoindexter]

DHeasley, had the same code on my 2001 2500 about 20k ago. was moving around 15 mph and it went to idle. shut truck down and restarted and everything normal. checked the code 121 and replaced the apps and all has been fine since. if i remember right the code is a idle validation fault code for the apps. hope this helps.