Engine/Transmission (1998.5 - 2002) Anatomy of an APPS

[Gary - K7GLD]

HEY - looks like we just MIGHT be on the way to eliminating the second most common of 2nd generation truck failures... Oo. Oo. Oo.

 

[mhenon]

The only possible glich in this Williams TPS is the way the IVS is wired. Polarity is reversed from the DC system. The pole on the Williams IVS is 5v where the pole on the OEM is ground. Looking at the schematic though I think the IVS is basically a dumb relay that takes its commands from the TPS circuit. Once the IVS trips to either the idle position or accelerate position it shouldn't care which way the current flows (he says with fingers crossed).

I really think it's going to work. Bob says it looks like it will bolt right up to the exsisting bellcrank assembly so very little fabrication is needed.

Anyway, let us work the bugs out and we should be able to supply a parts list to make the swap.

Mike

 

[mhenon]

Just a quick update to keep this thread going. I got the Williams Pedal assembly. Really nice, well made unit by the way. I had already cut the OEM wiring harness to the APPS plug and installed Weather Pack connectors. Weather Packs are the type of connectors used in the Williams Control plugs.

The voltage across the potentiometer when hooked up to the truck was way too low to trigger the IVS switch. What this means is the engine would idle just fine but voltage, even with the pedal at WOT, never got high enough to trip the IVS to allow acceleration. I think (I hope!) this will be easy to fix but have to play with it some more.

Have to leave things there as we're off visiting family for a few weeks. Bob is still working on his Williams TPS and may come up with a fix.

Mike

 

[mhenon]

Here's a little info on Idle Validation Switches (IVS) and their use in the TPS:

Integrated throttle position sensor with independent position validation sensor - US Patent 5321980

As you read through this you'll see that the IVS is sort of a safety switch to prevent a computer controlled engine from taking off (fueling) when you really asked for less or no fuel.

Mike

 

[rweis]

I have not had the chance to do the mesurements BUT:



The Wilson APPS ready for this:



The Wilson APPS IS AN E X A C T I mean an EXACT I mean EXACT fit to the APPS bracket.



I tried the fitment today and about fell over with excitement.



Gary sent me one of the extra brackets he had so I would not have to screw up my working DC APPS, THANKS GARY.



The Wilson APPS has a shoulder that goes into the hole in the DC APPS EXACTELY. Then I thought "well the mounting screws would not match". An EXACT match. THe APPS holes in the Wilson and the holes in the APPS bracket aligned perfectly and even the screws were the correct pitch and diameter. The screws screwed in with finger pressure.



UNBELIVEABLE!



Mike reported the APPS would start the engine but the IVS voltages are not right. Well a little voltage here and a little voltage there is workable, somehow, GARY listening?



I think we definitely have a possibility. The fitment is PERFECT virtually PERFECT.



More to come, but definitely excited!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!



The fitment is PERFECT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!



Bob Weis

 

[grass hopper]

don't mean to hijack this but could the apps i replaced about two months ago be going bad this soon. i got it new from the dodge house. how long of life do these thing have?



oh by the way mine will over reving (after it's up to temp) if you touch the pedal.

 

[mhenon]

I have not had the chance to do the mesurements BUT:



The Wilson APPS ready for this:



The Wilson APPS IS AN E X A C T I mean an EXACT I mean EXACT fit to the APPS bracket.



I tried the fitment today and about fell over with excitement.



Gary sent me one of the extra brackets he had so I would not have to screw up my working DC APPS, THANKS GARY.



The Wilson APPS has a shoulder that goes into the hole in the DC APPS EXACTELY. Then I thought "well the mounting screws would not match". An EXACT match. THe APPS holes in the Wilson and the holes in the APPS bracket aligned perfectly and even the screws were the correct pitch and diameter. The screws screwed in with finger pressure.



UNBELIVEABLE!



Mike reported the APPS would start the engine but the IVS voltages are not right. Well a little voltage here and a little voltage there is workable, somehow, GARY listening?



I think we definitely have a possibility. The fitment is PERFECT virtually PERFECT.



More to come, but definitely excited!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!



The fitment is PERFECT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!



Bob Weis

Great news Bob. I didn't have but about 20 minutes to test the Williams TPS on my newly re-wired APPS but the voltages across the board were way too low to trigger the IVS above an idle. Just for grins I fired the engine up and it did idle just fine but no acceleration.

When I get home I'll have to check my wiring (#1) and move on to the Williams TPS if that checks out. Off the top of my head I can think of 2 or 3 things causing the problem and a work around for each. Really hoping you and Gary will have the solution long before I make it back. Good luck!

Mike

ps:just curious..... how did it fit!!!!

 

[Gary - K7GLD]

HMMmmmm - well, if only a SINGLE operating voltage source is needed, there are options as to voltage regulators that could be used - IF that voltage doesn't have to originate from inside the ECM. That lead is tagged as pin 31 on my ECM schematic...



THEN, the remaining question is, if the ACTUATING voltage is increased, what will the resulting increased RETURN voltage do to the ECM?

 

[mhenon]

HMMmmmm - well, if only a SINGLE operating voltage source is needed, there are options as to voltage regulators that could be used - IF that voltage doesn't have to originate from inside the ECM. That lead is tagged as pin 31 on my ECM schematic...



THEN, the remaining question is, if the ACTUATING voltage is increased, what will the resulting increased RETURN voltage do to the ECM?

Gary & Bob, I think we need to power up an APPS with the 5 volts required and take some measurements as to output voltage/resistance. Then do the same with the Williams TPS. I made a simple little 5 volt power supply from one of our grandkids Gameboy wall plug-in adapters. I have a box full of these things ranging from 5 volts to 12 volts. The 5v adapter I used puts out 5. 6v unloaded and right at 5volts with a light load on it. Perfect for testing the TPS. I just didn't have time to run any comparisons between the two TPS.

Anyway, once we know what the APPS does under normal conditions i'm confident we can modify the Williams, if needed, to mimic it. . even if it takes a little tweeking electronically (I'm thinking of a possible interface board with additional, resistance, capacitance or relays to fool the ECM).

Let's stay on this as i'm very confident we have the part we need here. The price alone ($100 vs $400) is enough to make me want to pursue this to the end.

Mike

 

[rweis]

What I was thinking is the resistance traces are different values. Just have to measure both of them to see what they are and that should give us a direction to go.



And actually we need to get the WIlliams as close tothe OEM APPS as possible. You would not want to "give it a little throttle" and the APPS thinks you are requesting 2000 rpm. RATE of resistance will have something to do with it.



Bob Weis

 

[grass hopper]

What I was thinking is the resistance traces are different values. Just have to measure both of them to see what they are and that should give us a direction to go.



And actually we need to get the WIlliams as close tothe OEM APPS as possible. You would not want to "give it a little throttle" and the APPS thinks you are requesting 2000 rpm. RATE of resistance will have something to do with it.



Bob Weis

You would not want to "give it a little throttle" and the APPS thinks you are requesting 2000 rpm.



thats what mine is doing right now.

 

[KarlC]

What I was thinking is the resistance traces are different values. Just have to measure both of them to see what they are and that should give us a direction to go.



And actually we need to get the WIlliams as close tothe OEM APPS as possible. You would not want to "give it a little throttle" and the APPS thinks you are requesting 2000 rpm. RATE of resistance will have something to do with it.



Bob Weis

If the throttle potentiometer is really just a potentiometer like the schematic shows I don't think the total resistance of it will matter very much, within a pretty wide range. What would matter is how close to each end of the resistance element the wiper can get when going from no throttle to full throttle. I believe that's what the APPS calibration procedure is for, to teach the ECS what the voltage range is for the particular APPS.



What will also matter is that the IVS is wired up the same way. My schematic (in the DC 2001 manual) shows the IVS as a switch with one normally closed and one normally open contact. I suspect all that electronics in the stock APPS is there to utilize a potentiometer to simulate a mechanical IVS switch with the two contacts.



Karl

 

[mhenon]

I think our IC board in the OEM APPS does a little more than trip the IVS. It looks like it's giving two reference voltages to the ECU to better evaluate what the APPS is telling it.

check out this for a better explaination with schematics:Automotive Training and Resource Site

If that doesn't show the TPS pdf scrool down to tech article #33.

Mike

 

[Gary - K7GLD]

What will also matter is that the IVS is wired up the same way. My schematic (in the DC 2001 manual) shows the IVS as a switch with one normally closed and one normally open contact. I suspect all that electronics in the stock APPS is there to utilize a potentiometer to simulate a mechanical IVS switch with the two contacts.

On the APPS I took apart and pictured at the beginning of this thread, there is NO mechanical "switch" inside - I supect any "switching" is done instead, by a solid state sensor/switching device instead...



Perhaps that is what you mean.



One side of APPS internals:



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Other side:



#ad

 

[KarlC]

On the APPS I took apart and pictured at the beginning of this thread, there is NO mechanical "switch" inside - I supect any "switching" is done instead, by a solid state sensor/switching device instead...



Perhaps that is what you mean.

Gary,



Yes, that is exactly what I was trying to say.



Your photos are good enough I could almost draw a schematic of it. I can't tell what the numbers are on some of the parts and I can't see traces underneath components to see where they go, but other than that I could probably figure it all out.



Could you check something for me on the APPS you have taken apart...



I've done a little staring at the pictures, and I think I have a good start on a schematic. In the first picture, there are two groups of six traces going off the left edge of the board. Looks like the upper group goes to the resistance elements on the other side, and the lower group goes to the connector to the ECM. Looking at the traces in the lower group from top to bottom, I think they probably go to the following connector pins: 4, 3, 5, 2, 6, 1. These would correspond to APPS ground, APPS signal, APPS +voltage, simulated IVS switch 2 (closed for not idle), simulated IVS switch 1 (closed for idle), IVS ground.



If you can confirm that the traces hook to the connector pins as I think they do, that would mean I'm on the right track and can go a bit further in drawing a schematic for it.



Karl

 

[Gary - K7GLD]

WELL, that disassembly and pics was done quite a while back - and I don't have the unit any more - but the traces are pretty easy to figure out:



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Look at the above pic of the component side of the Mylar mounting strip, and the LOWER group of traces go directly to the pins of the APPS - the upper group folds back, and goes to the potentiometer trace side:



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There above, you can see 5 of the traces grouped, leading to the fold, and the other component side - not as easily visible in the above pic, is the 6th trace. running at the extreme left outer edge of that potentiometer trace, meeting up with the rest, for a total of 6 traces connecting the potentiometer to the components seen on the other side.



Clear as mud? :-laf



From what I can see, virtually all the smaller components are surface mount resistors and capacitors - the only active device I see is the integrated circuit, which apparently performs all active functions, and "translates" them to the control computer.

 

[mhenon]

Gary,



Yes, that is exactly what I was trying to say.



Your photos are good enough I could almost draw a schematic of it. I can't tell what the numbers are on some of the parts and I can't see traces underneath components to see where they go, but other than that I could probably figure it all out.



Could you check something for me on the APPS you have taken apart...



I've done a little staring at the pictures, and I think I have a good start on a schematic. In the first picture, there are two groups of six traces going off the left edge of the board. Looks like the upper group goes to the resistance elements on the other side, and the lower group goes to the connector to the ECM. Looking at the traces in the lower group from top to bottom, I think they probably go to the following connector pins: 4, 3, 5, 2, 6, 1. These would correspond to APPS ground, APPS signal, APPS +voltage, simulated IVS switch 2 (closed for not idle), simulated IVS switch 1 (closed for idle), IVS ground.



If you can confirm that the traces hook to the connector pins as I think they do, that would mean I'm on the right track and can go a bit further in drawing a schematic for it.



Karl

Karl... you getting an figuring that board out?

Mike

 

[mhenon]

"Karl... you getting an figuring that board out?"

I meant to say "anywhere". Getting anywhere on the schematic?

 

[KarlC]

Been really busy this week. Will get to it this weekend.

Karl

 

[rweis]

That would be pretty interesting to get the bus APPS for its hardware traces and mate an electronics package to it that would be as close as possible to the OEM electronics. Could be the best of both worlds.



Bob Weis