dewclaw

Has anyone ever tripped a PO121 code ? If so what was your fix for it ?

Its basically a electronic signal conflict between the MAP Sensor the Throttle Position Sensor and the computer. I also have an Edge EZ chip thrown into that loop too just to complicate matters . : To start with I guess I will take out the EZ for now and see if my problem goes away .

My symptoms of the PO121 code trip ?

Occasionally, only under light accelleration, the engine just dies or rather goes to an Idle .
(It doesnt seem to matter what gear its in (5 sp). At this time the "check engine" light comes on too.

When I depress the throttle two times it comes back to life everytime.

I was going to start by testing the MAP Sensor . Well, right off the bat , it takes a special diognostic gizmo to test it . So here I am hoping someone has some good advice for me .

Thanks in advance .

Brett

phox_mulder

APPS reset helps sometimes.
Follow this to the letter, no skipping steps.
https://www.dieseltruckresource.com/...n&onlynewfaq=1

If that doesn't fix it, or only fixes it for a short time, you can try a new APPS, but they aren't exactly cheap.

You could try replacing the CKP.
Not sure if the Crank or Cam position sensor feeds the computer the engine speed on yours,
as they did away with one of them in my year.
It/they are a little cheaper than the APPS.


phox

dewclaw

OK , I tried the APPS reset . I sure hope thats all it takes !

I will keep ya posted .

All other replies welcome !

Thanks ,

Brett

dewclaw

Well I reset the APPS and so far so good . Hope that was the fix !!!
Time will tell . I will keep ya posted .
Thanks ,

Brett

dewclaw

Well i did a 500 mile trip and it started acting up again . I think I will try what someone suggested and clean the internals of the APPS (TPS?).
Im just keeping you posted in case someone else runs into the same problem. Hopefully I/we will find the fix and keep me away from the dealership.

Any other opinions out there ?

Thanks ,

Brett

dewclaw

After reading some info Im thinking it is the TPS. The dealer wants $225.00. My bud at the parts place thinks he can get me one for $128.00. Not too bad I guess.
Another reason I think its the TPS is that it only happens at a certain "throttle position", that being minimum throttle.
I will keep ya posted on whether or not this is the fix in case someone else pulls a PO121 code and has the same symptoms.

~Brett