Engine/Transmission (1998.5 - 2002) APPS Question

[GIT-R-DONE]

I have a spare apps for my 02 H. O. ( since been sold ). Before I sold the truck, I checked the part numbers from one to the other and they were the same.

BUT... . on side of the apps, there is a VDC number and they didnt match up.



The one on the truck was 0. 452 VDC, and the spare was 0. 470 VDC. Is there a problem with these numbers not matching up? What is this number and how important is it? TIA

 

[nps]

VDC is a calibration number - how many volts DC the unit is outputting at rest.



The APPS reset procedure calibrates the ECM to read the APPS at full throttle and no throttle positions. Providing the APPS puts out a nominal minimum voltage, small differences won't matter.

 

[GIT-R-DONE]

So, its your belief that this would work ?

 

[fox]

So, does anyone know the range of voltage at idle that we should allow? If you found there is a best voltage to try for, what is that. What I am asking is, is it more responsive at the upper limit or lower.

Thanks.

 

[GIT-R-DONE]

After chatting a while with our local knowledgeable dealer..... some of these voltages are different and wont hurt anything. Part number matches up with the year and specifics of truck, so... . thanks for the advice and assistance of understanding more about these.

 

[nps]

So, does anyone know the range of voltage at idle that we should allow? If you found there is a best voltage to try for, what is that. What I am asking is, is it more responsive at the upper limit or lower.

Thanks.

There is no better voltage - only the right voltage. It is what ever it is when at idle. That's why the ECM gets calibrated when you reset your APPS - so it knows what voltage means you've got your foot off the pedal - for things like TCC on autos and engaging the e-brake.



The voltage variances due to are differences in manufacturing. As far as I know you cannot adjust the APPS.

 

[Todd T]

There is no better voltage - only the right voltage. It is what ever it is when at idle. That's why the ECM gets calibrated when you reset your APPS - so it knows what voltage means you've got your foot off the pedal - for things like TCC on autos and engaging the e-brake.



The voltage variances due to are differences in manufacturing. As far as I know you cannot adjust the APPS.

I'm dragging this back up after searching numerous posts on the topic. in the Anatomy or an APPS thread it was told that pin 3 had the ref voltage, pin 4 was ground and pin 5 was the wiper. OK?



Now we know each APPS has a foot off pedal, lowest it can read VDC on the label and the ECM calibrates to that. the book tells us not to adjust it in the slots. In the Anatomy thread it was discovered that the APPS can get a wear pattern and start to cause problems with eratic readings in that range. as in the area where your pedal is for most of the time the truck is in motion. good here?



Well what if we adjusted the APPS to read past that bad spot for it's Idle position and reset the ECM to calibrate to that voltage? we'd be eliminating the bad spot and if this ECM recalibrates to that output spot for idle (no one has stepped up with a idle voltage tolerance/range) this should work. Provided you dont go past the built in overtravel and lose your WOT ability. This could be the only problem I see with this method in a stock truck by not having the range (previous over-travel) left for full WOT power.



At my power levels my truck hardly sees anything over 25% of the throttle anyway. It would self destruct if I put it to the floor! I've monitored the APPS with my Auto Xray tool and on a, we'll call it WOT stomp, i cant get over 25% before I hit 70+ PSI of boost. I use very little travel of my pedal to get were i'm going at anytime. currently I'm at 8% for idle and cruise in the 17-19% range in 4th or 5th gears for a constant speed heading.



I often thought of increasing the fulcrum length on the throttle cable to take some sensitivity out of it for the bumpy roads. We need a detuned version of an APPS that would not be so sensitive across the board.



on that note is there a way to slow up the rate of increase through the range of rotation on the APPS? resistor possibly?

 

[Devil Black Diesel]

You're supposed to adjust your APPS voltage to match the number on the white sticker located on the back of the APPS. Just probe the orange wire with blue stripe that goes into the far right connector on the PCM with your key on (engine off). If it does not match the voltage on the white sticker on the back of the APPS then you need to adjust the voltage to match as closely as possible. Mine was . 516VDC so everytime I check mine I adjust it as closely to . 516 as I can.



Some are lucky enough to adjust the voltage with a Torx bit in the photo below, and other's will have to adjust the APPS by loosening it and rotating it. You have to be very careful not to strip the bolts while trying to unscrew the APPS... . you only have one shot at it.



There is another thread where someone took the time to explain this procedure in great detail, do some searching and you'll find it.

 

[RAJohnson]

Here is how to reset the APPS. Oo. Oo. Oo.



RESETTING THE APPS SENSOR.

(ACCELERATOR PEDAL POSITION SENSOR)

2ND GENERATION 24 VALVE TRUCKS ONLY.



LIST OF TOOLS NEEDED



DIGITAL VOLT METER

# 20 TORQUE BIT SOCKET

# 1 PHILLIPS

# 10 MM SOCKET



Proper service and repair procedures are vital to ensure personal safety of those performing the repairs. Standard safety procedures and precautions should be followed at all times to eliminate the personal injury or improper service, which could damage the vehicle or compromise its safety.

Although this material has been prepared with the intent to provide reliable information, no liability is assumed in reliance of this material.



It has come to my attention that a lot of people think by disconnecting & re-connecting the batteries and stepping on the throttle it is going to reset the apps, no, that is not correct. It is impossible to adjust your apps if you do not know where it is supposed to be set at. That is why you need the voltmeter.



This is the procedure I use to re-set the apps.



With the key on, engine off you need to probe the apps wire to see where your voltage is currently set at.

The best location to probe the wire is on the PCM (power control module) which is located off the passenger side of the firewall.



• You want the C1 connector, this is the connector closest to the engine,

• You want the orange wire with the dark blue tracer which is pin # 23

• Voltage should read 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 ***



• The apps sensor is located slightly above and a little to the left of the injection pump.



• Remove the black plastic cover that is located by your injection pump.



The two screws that are holding it are plastic, do not put any downward pressure on them or you will never get them off.



• Un do the 6 - 10 mm headed bolts that hold the bracketry in place.

(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 - 20 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 these screws strip very easily and you only get one shot at them.



• On the apps you will find a white tag that gives you the information on what the apps adjustment should be.



• After loosening the screws you can rotate the apps both clockwise and counter clockwise to get the adjustment you need.



• The reading you took at the beginning of the process on pin # 23 should match the white tag on your apps, if not adjust accordingly.

 

[azpete]

One thing to mention about the apps adjustment. Don't know if mine is just different or not but after setting as close as I could to the tagged voltage (very sensitive) screwing the cover back on would change the voltage by up to . 01 or more volts or more. After 5 attempts got within . 008 and called it quits.

 

[Todd T]

I understand how to adjust it. What I'm asking is if we have a bad spot in the APPS what would the harm be if we adjusted past that spot resulting in a higher than . 5-. 6 volt range most are tagged for, for idle?



I know on Fords EEC-IV and V systems . 601 is considered off idle and the PCM begins to fuel and add timing. You can set them as low as you wanted for idle as long as you could still get full range of motion which is . 601-4. 585 volts. the trick was to set them as close to the off idle voltage (. 601) as possible for best throttle response.



Our trucks have a huge overtravel range and with the mods most of us have they use even less of the range of rotation.



I'm saying move further into the range, past the bad spot (or suspected) and see if that alleviates the APPS problems, instead of buying the costly new one.

 

[Todd T]

After thinking about this some more, why not move past the bad spot and use a resistor to bring the idle voltage back into the . 4-. 6 volt range (whatever the tag reads now). This would get the ECM thinking all is well if there is indeed a spec voltage for idle not to exceed.



obviously, after moving it you'd have to reset the ECM to learn the new idle voltage for any of the above.

 

[nps]

Seems like what you are saying makes sense Todd. There are a couple of disconnects in the whole APPS logic however:



DTT (a respected and reputable source in the industry) says don't reset the APPS/ECM by disconnecting the batteries; you have to physically adjust the APPS to match the factory voltage tag. Does this mean every ECM is matched to a specific APPS? I think not. How then does the ECM 'learn' the correct voltage for it's given APPS? By the disconnect batts/press on pedal method? Seems logical. Or is there some other secret factory 'learning process' that has to take place? I need to look this up in my FSM tonight.



If you accept the preceeding and the disconnect batts method works, then why bother with the physical adjustment of the APPS? Isn't disconnecting the batts just like installing a new APPS with a different factory voltage? You are causing the ECM to 'learn' a new idle voltage. This is your premise for adjusting the APPS past the bad spot.



If you previously disconnected your batts (for whatever reason, including APPS reset), then use the physical adjustment procedure WITHOUT relearning the new idle voltage, then haven't you made things worse? Why isn't this scenario addressed in the DTT procedures?



The only thing that makes sense given experiences from TDR members is that both procedures work - resetting the APPS and physically adjusting the APPS. However it seems that the worst thing one could do is inadvertently reset the APPS (because batts are unhooked), then adjust the APPS to the factory voltage and fail to reset the APPS again.

 

[Todd T]

yep that's the very disconnect. no one knows if there is a set tolerance or if it just learns whatever the APPS is putting out. my guess is there's an off idle spec and probably somewhere near the . 6 volt range I quoted. maybe the idle validation switch (IVS) trigger voltage is what the tag/label is indicating and we should stay at of below this. That would be around the range I would expect it to trigger. somewhere @/below . 6 volts is the norm on most everything.



So If this is the case, then we could not move the APPS in its slots past where the IVS throws. Otherwise you would never come back to idle. I would need move the APPS in its slots past the bad spot, then with resistors bring the IVS voltage slightly lower than the wiper circuit voltage reading at rest, but still within the labeled voltage range. This way when you depressed the throttle you'd have a small range of rotation, trigger the IVS and from there start your throw of throttle input voltage. I would just need to pay attention not to run out of range of motion for WOT.



Sounds like a lot of work LOL

 

[nps]

Well I looked in the FSM and guess what! For both an ECM change and an APPS change you have to unhook batts (already done per R&R procedures), reconnect them, turn key ON, and then depress the accelerator and slowly release it to allow the EMC to learn the idle voltage.



The FSM makes no mention of the purpose of the voltage tag on the APPS - I suspect that it is for mfg purposes to record that this APPS was tested and is within spec.



While it seems that you can mechanically adjust the APPS back to the factory tag, the FSM would suggest that this is no more effective than the disconnect batteries, reconnect, key on and push pedal method.



However what is obvious is that anyone who does mechanically adjust their APPS should most definitely 'relearn' the ECM at the same time also.

 

[Bob4x4]

You can get carried away with the adjusment!There are 2 idle switches in the apps assy. The ecm looks at these not just the voltages. 1 switch is n/o the other is n/c. at idle. They use 2 as a redundant feature to make it more reliable. If you rotate the sensor or as 1 person suggested adjusting the throttle stop(not a good idea)too far the Ecm will not see an idle condition.



Bob

 

[runningbird]

My voltage doesn't change at all when i move the sensor around... does that mean mine is definetly bad? It sits at . 553, tag says it's supposed to be . 633.

 

[Bob4x4]

My voltage doesn't change at all when i move the sensor around... does that mean mine is definetly bad? It sits at . 553, tag says it's supposed to be . 633.

You loosened up the sensor mounting bolts and pivoted the sensor and it did not change?

 

[runningbird]

You loosened up the sensor mounting bolts and pivoted the sensor and it did not change?

that's correct. I loosened the two the go through the sensor and it was moving around freely; the voltage did not change at all.

 

[RAJohnson]

that's correct. I loosened the two the go through the sensor and it was moving around freely; the voltage did not change at all.

Are you sher your checking the voltage on the correct wire. I believe it is pin #23.