Engine/Transmission (1998.5 - 2002) code p0121..APPS problem???

[BSmalley]

This past week I had to make a fast turn around trip from northern NH to Savannah GA. We did 2,535 miles in three days and in the middle of that, packed up a house into a UHaul and brought it all back north. Was very happy with truck most of the way, but..... about an hour from home, the throttle seemed to just go dead. Had just replaced the lift pump three day previous. truck acted like no fuel, as it would cut in and out. stopped and picked up a fuel filter although had just put new one in. also put a bottle of power service 911 into tank. Truck started to run better with only very occasional skip. Got to beltway around DC and it started again. Pulled off onto exit to change fuel filter and truck died at end of exit ramp. . Didn't stall, just dropped to idleand would not go above 800 rpm. Check engine light came on (for first time). Checked and got the p0121 code. looked it up in the book and it says APPS low voltage. Shut truck down and when restarted after about 10 mins, engine light was off and truck ran fine. continued trip to GA and return, truck ran fine for just over 2,000 miles and as soon as I got back to the MA/VT state line, it started acting up again. Eventually made it home and the engine light came on again yesterday morning..... SO question is does this sound like the APPS unit itself is bad or could it be electrical? Is there any field tests I can do to check? Where is the best place to get the APPS if I need one? and how much $$$? The way I read the book about the voltage, I can't tell if it means there is low voltage going into unit or low voltage coming out of it. Any answers or ideas??? Thanks

 

[DLBurns]

Apps

Welcome to the ever expanding club of problem APPS owners!!

I have been experiencing the same problem just not as drastic as yours. I get the P-0123 code - switch "A" circuit high input??? WTF????

I have no idea what that means but have done alot of research on here about this problem..... we are not alone!!

I just cleaned all of the connections I could get to with a good contact cleaner and relubed everything with dielectric grease, also did the grounds. Haven't thrown the code yet.

I am not comfortable that this is the fix, Blair came over today and we checked the voltage going into the apps at idle and WOT. 0. 49 volts at idle and 3. 65 volts at WOT. Blair is checking to see if that falls into the correct parameters.

There is ALOT of information here on this problem, a member, Gary, did a great write up on the "Anatomy of an APPS" do a search using this title.

I don't think there is a way to fix this thing short of just replacing it ( which I am going to do once I am certain this is the problem I'm having )

Goodbye $400 smackers