Code PO 121 any suggestions?

[me4osu]

Every now and then, the rig acts like I completely let off the accelerator while I am pushing it with my foot or even in cruse control. Also the check engine light comes on.

Went to Auto Zone and their reader said P1693 (trouble code detected in ECM) and PO121 (accel position sensor volts do not agree with idle validation signal). I did a search on TDR and found the disconnect batteries then range the accelerator slowly procedure. Did that, and the truck still does the same thing.

Does anyone know what is causing the problem without my having to do a lot of diagnosis? Is it the APPS or the Crankshaft Speed sensor? Thanks for the help.

I only got one response to this on the TDR. I guess because it wasn't about twins, DDIIIs or what damn FP gauge to buy.

 

[ToolManTimTaylor]

Call Scott up at Mass Diesel. He may be able to find and Fax over the diagnostic test to run with a buddy on the APPS (Me and wheaties did mine) It sounds like the apps is dropping out (From 5 volts to 2 or less) during the 1/2 - 3/4 sweep.

 

[Dr. Evil]

You may want to try resetting the APPS again....it costs nothiung and is worth another try. Follow this procudure:

1. Set parking brake
2. Disconnect negative battery cables on both batteries
3. Turn ignition key to run(to drain any remaining capacitors)
4. Let truck sit for 30 minutes( this is the recommended minimum)
5. Return ignition to OFF position
6. Reconnect both batteries and secure, not a timed event
7. Turn key to run position(not start) and depress accelerator pedal slowly all the way to the floor
8. Allow pedal to return to top position slowly
9. Turn ignition switch OFF
10.Release parking brake

Good luck...let us know.

 

[RAF]

If that dosen't work,might try unhooking the EZ and see if it goes away.

 

[me4osu]

Thanks guys. I didn't know about letting the truck sit for 30 minutes, I just unhooked the batteries, ranged the accelerator and connected the batteries again. I'll try that procedure this weekend, then the voltage test if that does not work. As a last resort, I'll unhook the EZ (almost as bad as giving up ***).

 

[NAIL BENDER]

When you hook up the EZ again it will feel like your first time.

 

[truckstom]

Originally posted by NAIL BENDER
When you hook up the EZ again it will feel like your first time.

I had mine pulled for a week and a half, put it back on, felt new all over again....oh that feeeelin'

 

[me4osu]

Did Dr. Evil's procedure and made it all the way to Shreveport, LA today without the light coming on. So far so good.

 

[me4osu]

Originally posted by me4osu
Did Dr. Evil's procedure and made it all the way to Shreveport, LA today without the light coming on. So far so good.

Well, on my way back, the dam thing dropped out seven times. Looks like I'll be trying the diagnostic TMTT talked about. If I can't find it in my manual, I'll call Scott tomorrow.

 

[truckstom]

Get it figured out yet??

 

[MYTRNx3]

Originally posted by me4osu
Every now and then, the rig acts like I completely let off the accelerator while I am pushing it with my foot or even in cruse control. Also the check engine light comes on.

Went to Auto Zone and their reader said P1693 (trouble code detected in ECM) and PO121 (accel position sensor volts do not agree with idle validation signal). I did a search on TDR and found the disconnect batteries then range the accelerator slowly procedure. Did that, and the truck still does the same thing.

Does anyone know what is causing the problem without my having to do a lot of diagnosis? Is it the APPS or the Crankshaft Speed sensor? Thanks for the help.

I only got one response to this on the TDR. I guess because it wasn't about twins, DDIIIs or what damn FP gauge to buy.

You are having the EXACT same issue that I WAS having...

Here's the fix.. and much easier than I thought.

first off pop your hood... hahahaa


you need to locate the black plastic box that covers the acceerator cable - remove it. Then there is a plug underneath the silver housing. unplug it, if you can't - don't worry about it, you'll be able to.

there is a really nice "don't mess with me or your screwed" label on the silver box - ignore it, take the sucker apart. Inside will find another thing you can take apart, till you come to the TPS which is a black box looking thing, about as big as a pack of smokes

Take that sucker out and clean it with electrical cleaner, blow it out really well with an air hose - then put it all back together.

Oh and it also helps if it's really cold outside, and you have a friend accidently drop the TPS on the ground.

when it's all back together, then do the reset the APPS thing by disconnecting the batteries for 30 minutes etc etc...

I'll go into detail and take pics if you would like...

Kelley

 

[me4osu]

truckstom
No, we have just recieved around $90 million for our yearly budget here at work, so I haven't even had time to check this site.


MYTRNx3
Are you able to see the actual rheostat or potentiometer when you take it apart, or is it sealed within the plastic box? Do you take the whole aluminum piece off of the intake?

 

[truckstom]

WHOA!!!
That's some serious BOMBing money!!!


Good luck with the problem, and let us know what it is...

 

[MYTRNx3]

Originally posted by me4osu
truckstom
No, we have just recieved around $90 million for our yearly budget here at work, so I haven't even had time to check this site.


MYTRNx3
Are you able to see the actual rheostat or potentiometer when you take it apart, or is it sealed within the plastic box? Do you take the whole aluminum piece off of the intake?

wrong place I think all together... I'll take pics and send them to you... Nothing is sealed...

 

[2500cummins]

You cant see the rheostat, its inside but not completely sealed, you can get a little contact cleaner in where the pivot is. You dont need to remove the housing from the intake, the APPS is mounted to the back of the plate the cables and pivot are on.
One more thing, if your doing this on someone elses truck at 9:00 at night about 65 miles from a parts store, make sure and drop the damn thing on a concrete floor like an idiot right after they tell you they were just quoted about $400 for it, the look on their face is priceless :***: