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

[Gary - K7GLD]

I just wanted to thank Brad patterson for donating an apps bracket, he even paid shipping and to top that off he 2nd dayed to me!! Got it today, and right now i'm doing some brainstorming. Thanks again. Also thanks to everyone involved in this thread, it was definitely a motivation for me!

DITTO thanks to Scottlauer for the APPS bracket he sent for me to experiment with - his generosity will be repaid many times over to other TDR members, if we can come up with an easy and economical replacement for the DC APPS modules.



THANKS A MILLION SCOTT!



NOW, what I need is a picture of the accelerator pedal linkage as it attaches to the APPS bracket bellcrank - I think that in view of the several issues with the Ford unit(s) already in test, I'll try another angle, and use an inline (string) potentiometer. Looks like it would most easily mount right in the bellcrank area, and be far easier to inspect and service there if need be - but I need to know what other linkage/cables might be in that area that might interfere.



Any help?

 

[BradPatterson]

Happy to help, wish I could contribute some "brain work" on the project, but I'd be in over my head. I have a question for those "in the know" , after recalibrating the voltage per the sticker on the back of the apps and "resetting " the pedal is the voltage supposed to remain constant? I find that while driving the truck with the DVM hooked up the voltage never stays the same. My sticker says . 515 and when the truck is not fueling sometimes my votage returns to . 485 up to . 530? Is this normal? Just curious. Thanks... ... ... ... Brad

 

[mhenon]

Brad. mine was all over the place seconds after adjusting it. It stayed in a general range but never held the voltage I had it set to.

It seems to be good enough to satisfy the ECM that the pedal is really at an idle.

Mike

 

[rweis]

Well, tommorrow is APPS day. I am taking a day off to see what I can add to this discussion. Anyone going to be around tommorrow if I need to bounce ideas off someone? Pm me some phone numbers I can reach you.



Plan:

First - I went back through the thread and do not find anywhere anyone measured a good APPS in ohms and volts so we know what to compare to. EXACTELY what are targets in ohms and volts? The throttle stops on the APPS brackets obviously limit the travel. Can they be adjusted logically? (I know they can be adjusted mechanically)?I can measure the APPS resistances with the ignition switch off. I assume I can measure the wire voltages with the switch on and the engine not running, right?



Second - Some comments are about 500 ohms low end and 2500 ohms high end. My bus APPS is 257 low and 2090 high so I am going to put a 300 ohm resistor in series to bring the bus APPS up to 557 - 2390 ohm range. Resistor wattage say 1 watt?



Third - I also found somewhere that the IVS was 20 - 125 ohms. Bus is 10 ohms so I am going to add a 50 ohm resistor in series for the IVS to give it 60 ohms. Resistor wattage say 1 watt?



Once the resistances are "close to right" the voltages should be "close to right"



Fourth - measure bus APPS voltage at low end, should be about . 5xx volts



Fifth - measure bus APPS at high end, should be about 4. 5 volts



IF ALL SEEMS in line crank it up and see if the IVS allows throttle up and down.



Bob Weis

 

[KarlC]

Plan:

First - I went back through the thread and do not find anywhere anyone measured a good APPS in ohms and volts so we know what to compare to. EXACTELY what are targets in ohms and volts? The throttle stops on the APPS brackets obviously limit the travel. Can they be adjusted logically? (I know they can be adjusted mechanically)?I can measure the APPS resistances with the ignition switch off. I assume I can measure the wire voltages with the switch on and the engine not running, right?

The APPS that Rick sent me had a cal voltage of 0. 62V, and when I tested it the output was 0. 732V when the IVS switched to non-idle mode, and 0. 812 when it switched back to idle mode. This is probably something to shoot for as far as the adjustment of the IVS switch/bellcrank.



I think it would work fine to measure voltages with key on and engine not running.

Second - Some comments are about 500 ohms low end and 2500 ohms high end. My bus APPS is 257 low and 2090 high so I am going to put a 300 ohm resistor in series to bring the bus APPS up to 557 - 2390 ohm range. Resistor wattage say 1 watt?



Third - I also found somewhere that the IVS was 20 - 125 ohms. Bus is 10 ohms so I am going to add a 50 ohm resistor in series for the IVS to give it 60 ohms. Resistor wattage say 1 watt?

I think any size resistors would work. I think it would work just as well without them too.

Once the resistances are "close to right" the voltages should be "close to right"



Fourth - measure bus APPS voltage at low end, should be about . 5xx volts



Fifth - measure bus APPS at high end, should be about 4. 5 volts



IF ALL SEEMS in line crank it up and see if the IVS allows throttle up and down.



Bob Weis

Sounds good.

 

[rweis]

Ok, so far:

1. As written above the bus APPS fit is exact.

2. The bus APPS cranks and starts the engine and will accelerate it 1 time.

3. Codes:



Code: 0121 TP sensor voltage does not agree with MAP

DC APPS voltage on 21 over at the PCM is . 579 my error, pin 23, not pin 21

Bus APPS voltage on 21 over at the PCM is . 154 my error, pin 23, not pin 21

This should be adjustable with a resistor



Code: 0122 TPS sensor voltage is too low (well we knew that)



Notice NO APPS codes? Which I think means the range of the bus APPS is ok.



I put my good APPS back in and cleared the codes and it cranked and accelerated just fine.



I also cut the ECM harness and installed WeatherHead connectors.



1@ 3 set for the APPS and 1@ 3 set for the IVS. This way I can plug my good APPS in and drive it (I also installed the 2 sets of WeatherHead connectors on my good APPS plug).



I also installed 2 sets of Weatherhead connectors on the bus APPS so I can test it)



(3 complete male and female sets, 1 for the harness, 1 for the dc APPS, 1 for the bus APPS)



SO where does that leave us?



I think the bus APPS is a good way to go. I still have to figuere out the right resistance set for the IVS and probably do some adjustments on the APPS range, but I think the bus APPS is ultimately do able.



I did not immediately add the 300 ohm and the 50 ohm resistors. That is probably what the 0122 code is saying since the bus APPS had 10 ohms and I think the dc IVS range is more like 20 - 120. A resistor in the sensor line would of course raise the voltage, and because of the code 0121 I think I may do a variable resistor so I can set it where I want it.



The dc APPS has some mechanical rotation adjustment on it. I measured the low end dc voltage at . 177 volts and my high end is . 595 volts. The bus APPS does not have any mechanical rotation adjustment and therefore to get some adjustment a variable resistor might just be the thing to allow that adjustment.



Definitely in the test mode now. I will get a variable resistor and adjust the bus APPS exactely to the dc APPS and then see how the ECM likes it.



My APPS looks more like a bench bread board than a diesel engine part, hey, but I got PLEANTY of wire hanging around to be able to tweak this thing to where ever.



Bob Weis



Oh, when I get it done since my APPS is fine if someone wants the bus APPS and connectors we'll figuer out something ($$$)

 

[KarlC]

Just received a pair of APPS connectors from Batts Racing, from the link in a previous post. Looks like an exact match to the APPS connector.



There is a contact retainer that snaps into place. They way it came it would be hard to get back out again if there was a need to redo anything. I'll file the tabs off each side of the retainer so it will will be possible to get it out again. When the connectors are plugged together the retainers will be held in place anyway.



I ordered the gold-plated contacts. From an electronics point of view this circuit is "dry". This can lead to problems because the current is so low it doesn't punch through the slight bit of corrosion that's always there on regular contacts. Gold doesn't corrode so it doesn't have this problem. The contacts I got are supposed to be crimped onto wires but looks like they can be soldered OK.

 

[timbo]

Well i made some progress with the ford tps. I made an adapter for it, but added cam action to it. Notice in the picture the shaft roller bearing assembly (that operates the mustang tps) is offset torward the front. The input rotation of DC bell crank is 50 deg, the output of the adapter is 75 deg. Next i hooked up my 5v power supply and checked output voltage. . 58 idle position, 4. 0 WOT I'm thinkin 4v should be enough to produce full engine power. With my mods i only use 25-50% of the petal anyway. Well i'm going to drill the mounting holes and continue with the project. I'll be back with a progress report later.

 

[rweis]

I went to Radio Shack this afternoon and got a fist full of resistors.



Tommorrow I'll remount the bus APPS and start tweaking the IVS signal.



I think I'll also add 220 ohms to the 257 - 2090 range to get it a little more in the middle of the range of 2000 - 3000.



As soon as I can get the IVS to trip, I think we have a winner. I plan on working resistors until I match the existing dc APPS . 5xx and the ECM should not have any qualms about that.



Stay tuned.



Right now I think we have,

Gary working the string potentiometer,

Timbo working the ford APPS,

and me working the bus APPS



Now tell me TDR is not something special



Bob Weis

 

[Gary - K7GLD]

Just received a pair of APPS connectors from Batts Racing, from the link in a previous post. Looks like an exact match to the APPS connector.



There is a contact retainer that snaps into place. They way it came it would be hard to get back out again if there was a need to redo anything. I'll file the tabs off each side of the retainer so it will will be possible to get it out again. When the connectors are plugged together the retainers will be held in place anyway.



I ordered the gold-plated contacts. From an electronics point of view this circuit is "dry". This can lead to problems because the current is so low it doesn't punch through the slight bit of corrosion that's always there on regular contacts. Gold doesn't corrode so it doesn't have this problem. The contacts I got are supposed to be crimped onto wires but looks like they can be soldered OK.

I just ordered a plug from them as well - good idea on the gold contacts!



I just hooked up an ohmmeter to one of my spare used APPS units I mounted to the bracket Scott sent me. I had to guess at the proper rotating point for the APPS mounting bolts - and just centered it in the slots. Full resistance across the total potentiometer is 2600 ohms - WOT is 2000 ohms, and from the idle end to the wiper at idle position is 230 ohms.



Dunno how far off that might be from the properly calibrated setting, but in a little bit, I'll order a 2000 ohm straight-line potentiometer from Mouser, and if need be, I can easily add fixed resistance at either, or both, ends for more precise ohms/volts calibration.

 

[rweis]

When I had my APPS connector apart today it had gold contacts.



Thanks for posting the resistance readings, every little bit helps.



Bob Weis

 

[timbo]

Well i just went out in the garage and checked APPS voltage on Pin 21 at the PCM, at WOT, with the DC APPS. It was 5. 75 idle 4. 01 WOT. I don't think it was documented yet what WOT voltage actually was with the DC unit. If it was i missed it. I got the voltage dead on with the mustang TPS! Monday i'll fire the mill up and do the bolt pattern and that part will be done! I also ordered a watertight microswitch from MSC friday , so monday it will be here and i just recieved the factory style plugs. I'll have it on the truck soon!

 

[rweis]

I think I made a mistake, not pin 21 but pin 23 on C1.



The SM does not show anything for C1 pin 21



Bob Weis

 

[Gary - K7GLD]

Well, I got the potentiometers ordered from Mouser today, but might have to change my game plan as to what type I use. When it came right down to picking out an inline type pot, I found the only available choices in the 2K value were rather cheap types that I doubt as to long term durability and quality - but I went ahead and ordered 2 different ones of slightly differing physical characteristics.



But I also ordered a conventional precision rotary 2 watt pot that I'm more inclined to actually use - and the mounting style I plan to use is nearly identical for either style, so no big deal either way.



The microswitches have been here for several days, and I'm not real thrilled with them either (I bought 2) - they seem a bit too cheap and flimsy for this use, and I may use an upgraded one instead.



SOOooo, I still need to see a pic of the inner hardware connections as used on auto transmission APPS setups, so I can try to develop my own "Shadetree APPS" in a manner that will work for both manual and automatic transmission trucks.

 

[timbo]

I think I made a mistake, not pin 21 but pin 23 on C1.



The SM does not show anything for C1 pin 21



Bob Weis

Pin 23 is correct, I had already known it was the orange wire with blue stripe never really looked at the pin#.

 

[rweis]

Gary,



As bad as I am at taking pictures and getting them to TDR I'll try to do that tommorrow. I have the APPS cover off and have an auto and speed control.



If I can not get them to TDR I will email them to you.



Bob Weis

 

[KarlC]

I did some measurements on my truck today, which so far as I know has a good-working APPS. The calibration voltage marked on the APPS is 0. 511V. I measured the idle voltage at 0. 521. If I press and release the accelerator the voltage it comes back to varies by maybe 0. 05 volts. Don't know if this is normal or not. At WOT the output is 3. 781 volts. Here are some APPS voltages and RPMs with the engine running at no load:



0. 521V 800 RPM (idle)

0. 667V 875 RPM

0. 714V 1000 RPM

0. 750V 1100 RPM

0. 794V 1160 RPM

0. 823V 1250 RPM

0. 920V 1500 RPM



The IVS switch (pin 6) went from a low to high voltage when the APPS output rose above 0. 76 volts, and went back to a low voltage when the APPS output fell below 0. 72 volts. So it appears the IVS actuates around 1100 RPM with no load.



It appears the ECM presents a 47K resistance to ground to the APPS output. This could help predict what effect the resistance of the APPS will have on what the ECM senses.



I think I finally get what you guys have been saying about adding resistance to the APPS. Adding resistance to one or both ends of the pot makes perfect sense to match up its end points and range. Sorry for not getting it sooner.

 

[rweis]

It rained all day today (Saturday) and I did not get a chance to make any progress.



KarlC,



GREAT information. That kind of measurement is exactely what is needed. The bus pot was . 154 volts barefoot (the barefoot ohms were . 257 which gives . 60 amps (V=IR) which seems about right). Assumming that the I stays constant (most computer circuits it does), I put your data in a spreadsheet and extrapolated it out to 4000 rpm.



The V goes from your data (straight line extrapolated) out to 1. 47V @4000. Assumming . 6 I constant, the W goes from your data . 521V @. 313W out to 1. 47V @. 887W. which only gives a 12% safety margin @ 4000 rpm with a 1 W resistor used to adjust the voltage output of the APPS.



However, since most of us run below 3000 rpm (. 751 W) the 1 W resistor rating should be fine (the 1/2 W resistor rating would not be fine because @ 1500 rpm V=. 92 I=. 6 W=. 55, and most of us run over 1500 rpm).



So if the . 6 I holds true, then V=IR, I am trying to target . 595V (I=. 6) I will do a 1000 ohm 1 watt resistor (standard resistor value). That gives my bus pot a range of 1257 - 3090 ohms which I think I remembering measuring the dc APPS at about 1k - 3k ohms.



This is getting better and better. Now we are getting enough information to accurately work this puzzle.



THANKS for the data. I will get me a 1000 ohm 1W resistor and see if the I (amps) stays reasonably steady and gives the predicted output.



Bob Weis

 

[timbo]

I'm a little confused about adding the resistor theory. If i read the past couple posts correctly you are trying to increase return voltage from . 154 to the . 5 range. I was curious about this so i took my 5v power supply and my TPS sensor and added a 1k resistor (inline) to each of the wires one at a time. Note the sensor before adding resistence was. 58v. First i put it in the 5v supply line. Output from the return wire went down to . 47 as i suspected, a drop. Next i put it inline with the ground wire. Voltage jumped to 1. 47 output!!!! I then switched out the 1k with a 150 ohm and the voltage went from the . 58 to . 74!!! I am now a believer and like KarlC said, Sorry for not getting it sooner. After seeing it for myself, it makes perfect sense. It seems to me you need to Decrease neg input to increase Positive output,on the return wire. Bob i think your on the right track to increase the voltage. I'm not sure how the IVS switching is going to be affected though. It might just work, good luck!

 

[Gary - K7GLD]

WELL, in my case - and depending upon the actual full resistance of the 2K pot I will use (that's all that's easily and commonly available), and since the APPS units I have tested so far all seem to be in the 2. 5K range, I'll probably start with 200 ohms added to the idle side of the pot, and 300 ohms on the WOT side. Probably also add some . 01 bypass caps to suppress transients to both the pot and the IVS switch - not real sure about series resistors for the IVS - might also be a good thing for transient suppression...