APPs test procedure. Anyone have one?

4x4dually

4x4dually

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Does anyone have access to any documentation on how to accurately test the APPs on my truck? I'm seeing the % fluctuate on the display while holding a constant pedal around 18-20% so I'm thinking that the potentiometer inside is wearing out or something in the assembly is wore. It doesn't do this when the key is on and the motor is not running, only while the engine is on and everything is shaking to death.

Does anyone have access to a repair manual or anything that would give detailed instructions on how to tear one down, test it, and re-install it?

Muchas Gracias.
 
aint got no help for ya, but that pic you had this morning was pretty nice, i am waitin for it to be in my inbox:D
 
Who reported you? What a maroon (old bugs bunny).

As far as I know jory it requires a screwdriver and some careful tinkering but nothing to bad. Just take yours apart. Just be careful not to jam the screwdriver in there and break it. LOL
 
Tyler, I KNEW that would come from someone! :bang :hehe: It works it just seems to have a "bad spot" in it where the resistance is affected by vibration. I know I can't possibly hold the pedal constant in this old brick wagon but when I hold it as close to constant as I can after a few seconds it will jump back and forth from 17 then 22 then 18 then.... The Attitude display doesn't really reflect the change near as much as my new Power View monitor. It also reads in 10ths of percentage so I can really see it bouncing. Now I just have to figure out is the variation is a result of the APPs being bad or the display being flaky or the data coming from the ECM being flaky. I think I'll hook a DMM to it tonight and shake the hell out of it and see if it stays constant. If you are driving down the road at about 20% throttle and hold the pedal, after a few seconds the engine will lose a little bit of power and you can see the throttle position go down on the monitor. I really hate to buy an APPs so I want to be absolutely sure that is the problem. Where's my screwdriver... :hehe:
 
I read where you can drill a 1/8 hole in the side of the sensor opposite the plug connector to spay some electrical contact cleaner on the brushes and contact pad, then plug the hole with some rtv. Kind of a last resort kind of thing.
 
I think I might clip a DMM onto the sensor output wires and put the DMM in my cab and read the actual voltage while driving down the road. I can also try to hold the pedal constant and record min and max voltages. That should tell me whether it is the sensor or not. Everyone at my house is sick so I will have to wait a day or four to work on the truck.
__________________
 
APPS

Instructions:

Tools: Digital Volt Meter, T-20 Torx bit, #1 phillips, 10mm socket

With the key on, engine off you need to probe the APPS wire to see where the voltage is currently set at.
The best location to probe the wire is on the PCM (Power Control Module) which is located on the passenger firewall behind the air intake.
You want the C1 connector, this is the connector closest to the engine
You want the orange wire with a dark blue tracer which is pin #23 (Please use a suitable backprobing adapter for your meter lead, do not pierce the insulation as this can lead to water intrustion/corrosion.)
Voltage should be somewhere around 0.5 volts,
At this point the voltage reading does not matter, it just has to be accurately written down for later reference

TURN THE IGNITION OFF ON THE TRUCK

Remove the black plastic cover off of your APPS. There are two plastic screws. One on the top and one on the front facing the radiator. It takes a little prying to pull it off.

Undo the 6-10mm bolts that hold the bracketry in place but DO NOT REMOVE THE CABLES!!

You will notice the APPS is on the back of the bracketry that you just removed, it is held in place by 2-T20 torx bit screws. These screws have a little bit of locktite on them so make sure you have a good socket and gently give a little tap with a hammer before attempting to loosen. Be very careful because these screws strip VERY easily and you only get one shot at them (VERY VERY VERY IMPORTANT; They are VERY tight).

On the APPS you will find a white tag that gives you the information on what the APPS voltage should be.
After loosening the screws (do not remove) you can rotate the APPS clockwise or counter clockwise to get the adjustment (towards the front of the truck increases voltage and towards the rear of the truck decreases voltage)
The reading you took at the beginning of the process on pin #23 should match the white tag on your APPS. If it doesn't the adjust accordingly.
 
Thanks for the post. However, my APPS does work except for that small range where it is messing up. I will check it per the proceedure but adjusting the output voltage to .5 VDC at baseline will only move the entire voltage scale up or down and affect the bottom or top end. If the scale it too high or too low it will throw a DTC of high or low voltage respectively. No codes here.
 
4x4 dually. Mine might be a fuel trouble. Is your fuel system stock. Fill out your cig.
 
Stock LP relocated behind cab on frame rail with Vulcan Big Line kit. Fuel pressure is 13-14 normal never below 10 psi at WOT. I know mines not a fuel problem.

And I usually delete my sig after posting in a thread after the first time to save space and redundency.
 
I saw it afterward. I was wondering if it might be the case because mines still stock. I havent figured out how to do that trick yet. Yes sir we may have the same trouble. BLOWIN SMOKE might give me a hand with this but if you figure out anything let me know. Im headin to flordia on wednesday and would like to have this fixed. I dont wanna be stuck half way there.
 
4x4dually said:
Stock LP relocated behind cab on frame rail with Vulcan Big Line kit. Fuel pressure is 13-14 normal never below 10 psi at WOT. I know mines not a fuel problem.

And I usually delete my sig after posting in a thread after the first time to save space and redundency.
Click to expand...



FYI Jory you should be able to go into the UserCP and fill out the sig, and click on the option to only show sig in the first post in a thread. Saves a bit of scrolling.
 
4x4 dually have you figured it out ? I havent had time and am green behind the ears on this so outside help would be appreciated.
 
Man, I need more hands and more time. The baby has been sick, the wife has been sick, and all weekend was spent setting trusses on a buddies new house and decking the roof. It was nice being the SkyTrak operator though instead of a truss monkey! At least I got out of a good percentage of the manual labor. Hoiwever I'm so sore I can't hadly move but I do have a little bottle of Hydrocodones here so I might be fine in about an hour! :D I want to buy a APPs from one of the two guys that have offered them to me and just try it. I think that is the only way to really find out for sure. What would you do, buy a used one with 25K on it for $100 or buy a used one with 2500 on it for $200? I like the price of one and the "newness" of the other! :bang Decisions decisions. The wife gets paid in a day or two and I may just pull the trigger on one of the two. And you can bet that when I get another one I'm gonna tear this old one down and see what the heck is wrong with it. I would imagine just 'wore out' will answer my questions.
 
i did exactly what you were talking about,,hooking up a meter on the line coming off the sensor,then i had another thought and hooked it over at the pcm and checked it again..i drove it and got right in the studder spot,,no fluctuations at all.rock solid readings,smooth as glass.....ive done the same on my map sensor,its smooth also.....the only way to get rid of my studdering,is to get rid of the timing...no more timing for me,and no more studdering......tst comp for me now,as i ran for years before,..sometimes its better to just stick with what works,,you know?............bama
 
I agree, I think the suddering is due to timing, but the problem here is a different animal. It doesn't shudder in the bad spot, the engine rpms flutuate.
 
Jory PM me an address and a phone number and I will ship you my old APPS, I just replaced mine and my stocker still works and you can test it out.

I replaced it for 2 reasons...1 is that I could be rolling down the highway at 55-60mph steady pedal and jsut bam I get dead pedal (the cheaper/APPS related one not VP44) and would set a code saying APPS input does not match boost. Sometimes it would happen 3-4 times a week, others it could go 2 weeks or more without happening.

Also when I hooked up my redline, it was seeing low voltage with the key on/at idle and needed to be adjusted but I had already bought a new one and it works flawlessly so I'm good now.

Like I said it would cut out every now and then, just push the clutch in and pump the pedal once or twice and it came back. But it worked just fine about 99.5% of the time and the low voltage at idle position may or may not have anything to with it cutting out.
 
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