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

[KarlC]

That's what I thought, and that's what makes me confused. The idle validation switch logic on my OEM APPS seems backwards.



It seems everyone agrees that pin 6 on the Dodge wiring harness Deutsch connector is for idle and pin 2 is for throttle. Referencing the corrected APPS/IVS wiring diagrams posted earlier in this thread, it suggests that the idle validation switch connected to pin 6 should be *closed* when the APPS is in the idle position. Since I'm measuring voltage on that pin when my OEM APPS is at idle, it means the switch is in fact open... just the opposite of what I expected it to be!



Likewise, I thought pin 2 for throttle should be open at idle and closed when the APPS is not at idle. Since I measure voltage on that pin when the bellcrank is open, it also means the switch is open when the bellcrank is open... completely backwards from what I thought.



So what's going on here? The idle validation switches are OPEN during the tested state?



Maybe I should cross check my voltage measurements one more time to be sure I didn't write things down incorrectly, but I swear I checked them several times each already because I couldn't believe what I was seeing.

John,



A while back I tested pins 2 & 6 on my truck with stock DC APPS. Here's the results, from post 469 of this thread:

With key on, engine not running, and a working DC APPS installed: pin 6 was near ground at idle and +5V when off idle. Pin 2 did the opposite.

Since each switch is pulling its line to ground, the switch on pin 6 should be closed when at idle, and the one on pin 2 should be closed when NOT at idle.



I've got a vacuum leak to fix on the truck tomorrow. If I have time I'll do another check of this just to be sure.



Karl

 

[JLandry]

Since each switch is pulling its line to ground, the switch on pin 6 should be closed when at idle, and the one on pin 2 should be closed when NOT at idle.



I've got a vacuum leak to fix on the truck tomorrow. If I have time I'll do another check of this just to be sure.

Thanks Karl.



And if the weather improves this weekend (we have wet snow right now in the Seattle area), I'll check mine again too. I must have incorrectly written things down when taking my measurements.



Regards,



John l.

 

[JLandry]

I would make a spreadsheet

Thanks Bob... I'm doing that now... having your data for comparison is very informative.

IVS range 3% - 10% (calculated)



My idle set point range is . 5 - 1. 0 my actual is . 527,



my IVS is . 620 - . 836 with 6. 5% @ . 728 my actual is . 702

OK, now I have a question about calculating the allowable IVS state change voltage based on the SAE specifications.



SAE J1843 states:

8. 2 Idle Validation Signal

8. 2. 1 LOW IDLE STATE—The Idle Validation Signal (IVS) shall be calibrated to change state at a point between 3 and 10% of the APS output span above the minimum APS position output. The IVS shall remain in the low idle state below this transition point.​

I interpret this to mean you take the 3% to 10% of the measured output span, and add that result to the minimum calculated SAE allowed APS position output, *not* the measured APPS idle voltage.



If I'm not mistaken, you used your measured voltage for both.



Am I nit picking? Maybe... but I just want to make sure we do this right.



Thanks,



John L.

 

[JLandry]

Sometime You Get Lucky!

Today I went back and re-checked the IVS function of my OEM APPS and all is well. It turns out I just made a mistake when taking notes. Pin 2 (throttle) shows voltage present at idle indicating it's electronic "switch" is open, and Pin 6 (idle) is just the opposite with the switch being closed at idle. With this information confirmed, I decided to remove the original working OEM APPS and in its place install the new Williams Controls APPS (part number 131856). I'm happy to report the new Williams APPS fit perfectly.



The next step was to measure the voltages of the Williams APPS with the engine off and without adjusting anything. Here's what I recorded:



DB/WT wire, pin 5 (sensor supply)

4. 96 VDC​

LB/BK wire, pin 3 in connector (sensor signal)

Idle - . 671 VDC



WOT - 3. 85 VDC



That makes the voltage span 3. 179 VDC​

LG/DB wire, pin 2 (IVS throttle active)

. 938 VDC on sensor (pin 3) when opening, . 885 VDC on sensor (pin 3) when closing​

BR/OR wire, pin 6 (IVS idle)

. 750 VDC on sensor (pin 3) when opening, . 730VDC on sensor (pin 3) when closing​

In taking these measurements, I noticed an interesting phenomenon with the IVS circuitry in the Williams APPS. When its electronic switches open or close, they don't do so as abruptly as what I had observed with the OEM APPS. Since I used an analog voltmeter to observe the IVS switches opening and closing, I noticed the voltage changed more gradually from one state to the other with the Williams APPS. In fact, I found I could even hold the IVS switch in the middle of its open or closed state with the bellcrank. The OEM IVS switch more quickly "tripped" from one state to the other.



Anyway, since the measurements were all well within the SAE J1843 specifications, I decided absolutely no adjustments to the Williams APPS were necessary. I did the APPS learn procedure one time, started the engine, and it works perfectly! A short test drive around the block confirmed no codes whatsoever. The only thing I can feel different with the Williams APPS is that the accelerator pedal travels slightly further from the idle position before the engine rpm starts to increase. I think this is consistent with the Williams IVS throttle active signal being at a slightly higher voltage above idle when compared to the the OEM APPS.



Anyway, I plan to continue to test drive the truck and will report more soon.



Best regards,



John L.

 

[JLandry]

The voltage on the sticker should match the reading you take at pin #23 on the PCM. I assume this is the same as pin #3 (signal or wiper) on the OEM APPS but won't say that for sure. Just go to pin #23 on the PCM and check your idle voltage.

Mike,



I was prepared to check APPS voltage on pin 23 of the PCM today, but before I did that I decided to check the wiring charts to be sure I understood how that pin was related to the APPS circuitry.



Well it turned out I couldn't find any relationship between pin 23 of the PCM and the APPS in a diesel powered truck. In a diesel powered truck the APPS signal is connected only to pin 25 of the ECM. However, in a gasoline powered truck, the APPS signal IS connected to pin 23 of the PCM.



Did you mean pin 25 of the ECM all along, or is there something else going on?



In any case, I found checking the APPS signal at pin 3 of the APPS Deutsch connector easy using a paperclip.



Thanks,



John L.

 

[rweis]

.....



Anyway, since the measurements were all well within the SAE J1843 specifications, I decided absolutely no adjustments to the Williams APPS were necessary. I did the APPS learn procedure one time, started the engine, and it works perfectly! A short test drive around the block confirmed no codes whatsoever. The only thing I can feel different with the Williams APPS is that the accelerator pedal travels slightly further from the idle position before the engine rpm starts to increase. I think this is consistent with the Williams IVS throttle active signal being at a slightly higher voltage above idle when compared to the the OEM APPS.

I found the same thing, a little more pedal travel before the ECM allowed the "throttle" good to go signal be sent to the VP44. When I put the micro switch in that is correctable because you are adjusting the micro switch seperately from the APPS pot.



Bob Weis

 

[rweis]

I towed the 5er RV this weekend about 200 miles and had about another 100 miles of unloaded driving. Absolutely zero problems with the micro switch IVS and the Williams APPS pot. Been running this way about 2 weeks now with zero issues. Very Very pleased, final solution for me.



EDIT added -



The VP44 blower also blows up into the APPS cavity and I drilled 3 holes in the top of the APPS cavity to get rid of the heat. I think that is going to be a MAJOR contribution to the longevity of the APPS regardless of who makes it.



I've been thinking that addition of the VP44 blower is significant to the VP44 longevity as well as the APPS longevity by keeping them flooded with OAT while running and even after shutdown (where the most damage could be done by heat soak).



Bob Weis

 

[mhenon]

... Did you mean pin 25 of the ECM all along, or is there something else going on?



In any case, I found checking the APPS signal at pin 3 of the APPS Deutsch connector easy using a paperclip... .

John, No. . I meant pin #23 PCM. It's proably the same reading you're getting at pin #3 on the Deutsch. Sounds like you're on top of this thing anyway. I wouldn't get too hung up on the voltage/resistance variations from one APPS to another. The ECM seems to be a little forgiving in this area.

Mike

 

[mhenon]

I towed the 5er RV this weekend about 200 miles and had about another 100 miles of unloaded driving. Absolutely zero problems with the micro switch IVS and the Williams APPS pot. Been running this way about 2 weeks now with zero issues. Very Very pleased, final solution for me.



Bob Weis

Sounds good Bob. I've been running about a month with the Williams and no problems so far. Hope this is the final solution!

Mike

 

[KarlC]

I found the same thing, a little more pedal travel before the ECM allowed the "throttle" good to go signal be sent to the VP44.

Might be possible to correct this by adjusting the the bellcrank idle stop setscrew in a bit and recalibrate. That way it wouldn't have to travel as far before the IVS trips.

 

[rweis]

I can agree with Karl's statement above because when I set my idle voltage I had to screw in the idle stop screw quite a bit (see pic in earlier post to this thread) about 1/8" - 3/16". My idle stop was at . 440 volts and I had to turn the idle stop in about 1/8" before the voltage started to climb which I think means there is a good bit of dead head travel before the voltage starts to climb toward "normal" of about . 600 volts or so.



That would translate into non reactive pedal linkage.



Bob Weis

 

[JLandry]

John, No. . I meant pin #23 PCM. It's proably the same reading you're getting at pin #3 on the Deutsch. Sounds like you're on top of this thing anyway. I wouldn't get too hung up on the voltage/resistance variations from one APPS to another. The ECM seems to be a little forgiving in this area.

Mike

Mike,



You're absolutely right and I stand corrected!



I went back and studied the wiring diagrams again so I could better understand this situation and now I see that pin 25 of the ECM receives the signal from pin 3 of the APPS, then apparently the ECM sends that signal back out on pin 28 to pin 23 of PCM connector 1. Very interesting.



Just for fun one of these days I'll check to see if the voltage present on these two wires is exactly the same.



Best regards,



John L.

 

[mhenon]

I can agree with Karl's statement above because when I set my idle voltage I had to screw in the idle stop screw quite a bit (see pic in earlier post to this thread) about 1/8" - 3/16". My idle stop was at . 440 volts and I had to turn the idle stop in about 1/8" before the voltage started to climb which I think means there is a good bit of dead head travel before the voltage starts to climb toward "normal" of about . 600 volts or so.



That would translate into non reactive pedal linkage.



Bob Weis

Bob, that makes me think that the bellcrank assembly (not the APPS) is slightly different for the automatic. I backed my idle stop screw all the way out and still couldn't get idle voltge below . 630v or so on the Williams APPS. Yet on the WM526 pedal assembly idle voltage is right at . 600v (same sensor).



Wonder if there's slightly more degrees of throw (idle stop to WOT stop) in the auto's vs manual bellcrank? Just a thought. I never could figure out how you were getting voltages below . 500v but maybe the auto's the answer.



Anyone know the parts numbers for the different bellcrank housing? That would tell us right there.

Mike

 

[BradPatterson]

Mike, when I get to the shop in the morning I'll look through some old invoices and see if I can get a part number for you, I have an automatic. Like you guys, my apps from Timbo has not skipped a beat!... ... ... . Brad

 

[rweis]

It's working and it's spreading, the more it spreads the more testing gets done.



Every new Williams we get into the Dodge we add another grain of sand to OUR pile and take one FROM DC's pile.



Bob Weis



Maybe the auto bell crank IS different than the manual. That would be an interesting twist.

 

[timbo]

Bob, that makes me think that the bellcrank assembly (not the APPS) is slightly different for the automatic. I backed my idle stop screw all the way out and still couldn't get idle voltge below . 630v or so on the Williams APPS. Yet on the WM526 pedal assembly idle voltage is right at . 600v (same sensor).



Wonder if there's slightly more degrees of throw (idle stop to WOT stop) in the auto's vs manual bellcrank? Just a thought. I never could figure out how you were getting voltages below . 500v but maybe the auto's the answer.



Anyone know the parts numbers for the different bellcrank housing? That would tell us right there.

Mike

I have a bellcrank for both and the travel is exactly the same. Bob might have a diff sensor than us. I've bench tested every sensor so far about 12. When the sensor is off the bracket and all the way at the and of the travel, voltage is 0. Then using a straight screwdriver, Begin to rotate it clockwise about 2 deg, voltage comes up to . 62-67 (THEN VOLTAGE STAYS EXACTLY THE SAME for about 4-5 deg of rotation then it rises as normal. That is why JLandry has a to move the petal slightly to begin to Rev up. I bench test using 3 voltmeters, wired into a male duetz plug, 1 to read voltage,1 to read Idle continuity,1 to read OFF idle continuity. I then bolt it up to the bracket and watch it perform on the meters.

 

[rweis]

I've been thinking about this also, why the difference in voltages between mine and others.



I think I have a DTT noise filter package connected to the PCM to prevent the transmission from hunting between 3rd and O/D. I think it may be connected to pin 23 on one end. I'll check it tommorrow. IF it is in parallel, then that would explain the lower voltages maybe?



----------



From the DTT web site:



Symptoms : Transmission shifting in and out of gear or TC locking and unlocking under light to medium conditions between 40mph-60 mph. You can very often address many of the above symptoms by doing the following :



Look for any ground straps or electrical connections that may be loose or contaminated. Check battery terminals, look for bad chassis grounds, bad PCM connections , bad ECM connections.



This is a minor electrical glitch that is a pain in the butt and causes many transmission failures.



It can take a good 4- 5 hours to properly go over all the above I have mentioned.



In addition to the above we developed the DTT Noise Filter. We have been testing it for over a year in house and via our dealer base. It has addressed over 80% of the electrical noise we have encountered.



Here is what we found :



Testing has shown alternator noise spikes present in the TPS signal to the PCM. These noise spikes may be responsible for improper operation of the lockup circuit and/or the overdrive circuit. The more load on the alternator ( ie air conditioning , charging a low trailer battery etc. ), the higher the amplitude of the spikes.



The main cause of this is the fact that Dodge has run the TPS harness wiring along with the alternator wires and noise is induced as a result. Testing has shown that the noise is not present in the TPS power supply from the PCM.



We were looking for an ecnomical filter system to try and address the electrical noise issues in these dodges. The DTT noise filter was a result of our testing.



----------



Bob Weis

 

[BradPatterson]

I've got the DTT noise filter too Bob and my idle voltage is . 610... ... ..... Brad

 

[mhenon]

This just gets curiouser and curiouser. Can't figure how Bob's idle voltage ever got that low. Doesn't matter really as he has it working. . but it would be nice to know what's going on there.



Brad, you say your idle voltage is . 610v. Is that as low as you could get it? If not whats the lowest you could get with the idle stop screw?

Mike

 

[Gary - K7GLD]

Been gone for a few days - looks like lots of - UMmmmmmm, INTERESTING stuff has been happening... :-laf:-laf:-laf



ANYWAY, got my own Williams APPS to play with, and a couple more test APPS brackets should be arriving - possibly sitting down at the post office as I write this



I ordered the Williams #131032, probably the right APPS module, but includes a fancy Billet-type CNC mount that is certainly NOT needed for our application, and drives the price higher - need to find out PRECISELY what the Williams # is for the APPS module ONLY, without any added and unneeded garbage attached...



Gotta get to NAPA to see if a proper 6-pin connector is available locally for connection to the Williams APPS - I have all the other stuff to complete another working replacement APPS assembly, bracket and all...



I want to continue working on simplified MS brackets for those who, like me, prefer to isolate the IVS function from the APPS module, and make it a mechanical operation, rather than electronic.



Still more to come...