APPS voltage Adjustment - Stopping the Myths!

[Mopar1973Man]

Ok Gang...

I just had a wonderful phone conversation with Rburks this morning and his chasing his problems with his idle well he happen to mention the fact he did the APPS voltage adjustment and I like "OMG not again!" There is a article on the Internet that is wrote up wrong and need to be corrected and stopped.

Problem #1 - Voltage on label

Everyone is trying to hit this voltage dead on... DON'T! This is the voltage that the APPS sensor goes from ON idle start to OFF idle state. You voltage MUST be BELOW this number.

Like on mine the voltage is .519. Don't set the voltage at this set it below this mark say .480 to .490 because as you add in voltage gain or loss during normal operation of the truck it might cross the mark and go off idle and you end up with idle set at 950 to 1000. Then find out your exhaust brake, high idle and a few other things don't work!

STOP! Don't set the voltage to the voltage on the label this is WRONG!

Like the timbo APPS you adjust to to the point you cross the dead zone and back off below this point 1/2 turn. Reason why is to keep the APPS from accidentally going to OFF idle state. As long as the voltage in the APPS sensor is below this state the the ON idle signal is given to the ECM and the APPS signal is basically ignored and idle programing is used.

Like for my example here the voltage on the tag is .553...

Now if the alternator or voltage of the system change a little bit you going to have issues of the voltage crossing back and forth over this boundary. Please set your voltage BELOW what on the tag by about 0.020 volts to insure the voltage is low enough to put the APPS sensor in ON Idle state.

Problem #2 - Where to measure the voltage?

I do know why they started measure the voltage at the PCM in concerns of the TQ Conv Lock up problem but this is wrong too. Now if you go over to my wiring diagrams here...

http://mopar.mopar1973man.com/cummins/2ndgen24v/wiring/wiring.htm

And now look at Page 1 and look at the PCM on the right at pin #23 you see its labeled ACC PEDAL POS. You think this is tied to the APPS?! Nope... Now switch back to page 3 now at look at the ECM on the right you find the wire at pin #28 on the ECM label ACC PEDAL POS SENS... But now look at all 3 pages this this Orange/Blue wire doesn't connect to the APPS sensor at all but it does pass the information to the PCM after it passes through the ECM (if there is any processing). So now look at Pin #25 on the ECM and you'll see it has a direct connection with the APPS. So if I was going to adjust the stock APPS sensor for voltage I would measure right at the APPS sensor or at the ECM pin #25 which happen to be Light Blue/back wire pin #3 on the APPS.

STOP! Don't measure your APPS voltage at the PCM this is WRONG!

Measure the APPS voltage at the APPS like Timbo does to if your going for better measure it at the ECM. By the time you measure the voltage at the PCM there might be a minor voltage loss so the voltage at the ECM will be high so hence most people complain about high idle, and other issues!

Problem #3 - How to adjust the APPS sensor?

There is no need to yank the sensor apart and mess with the 2 torx screw on the back you can obtain all the adjustment you want in the set screw on the bellcrank. But once again don't adjust for the voltage marked on the label... Make sure to flick the throttle bellcrank to WOT ans let it snap back to idle a few times and check you voltage again if the voltage is changing constantly the APPS sensor is wore out and no amount of adjusting is going to fix this problem.

STOP! Don't bother messing with the 2 torx screw just adjust the set screw on the bellcrank.

[rburks]

Great Write-up Michael, lot of problems reported on these forums are associated with this

Tomorrow,..if i get a chance i want check voltage at PCM and then at the APPS and calculate the difference....

Richie

[Mopar1973Man]

Great Write-up Michael, lot of problems reported on these forums are associated with this

Tomorrow,..if i get a chance i want check voltage at PCM and then at the APPS and calculate the difference....

Richie

Actually once again there is no reason to adjust the APPS at the PCM... PCM has no bearing on the engine... The only thing the PCM wants to see is throttle position for Auto Trans shift reason and it feed throttle information to the ECM for cruise control...

Still and all the ECM is more important to get the value right... Which is setting the APPS below the set on the tag... Anywhere below...

[rburks]

Michael, I know.. I am just curious is to how much drop there is...as we discussed over the phone hhen i first put the DVM on pin#23 org/blk wire at PCM connector my voltage was 0.314 so thinking it was low compared to o.448 printed on tag on rear of APPS i ajusted to Aprox. .447-.448 @ the PCM and it made no improvement infact i think it may have been worse...i tinking that the .314 was real close to begin with if messured at APPS or ECM.... I need to recheck it anyway and use the wire @APPS to get it correct using your method:smart: Richie

[Mopar1973Man]

Any news on this?

[dripley]

mike,

i am going to calibrate my tps today. checked my tps for the voltage and ther is not one on my new one. ther is on my old one. my new one came from blue chip diesel and is made by williams controls. ever heard of them before?

ripley

---------- Post added at 11:11 AM ---------- Previous post was at 11:09 AM ----------

by checking for voltage imean the sticker on the back like my old one has. my new one does not have one.

ripley

[Mopar1973Man]

mike,

i am going to calibrate my tps today. checked my tps for the voltage and ther is not one on my new one. ther is on my old one. my new one came from blue chip diesel and is made by williams controls. ever heard of them before?

ripley

---------- Post added at 11:11 AM ---------- Previous post was at 11:09 AM ----------

by checking for voltage imean the sticker on the back like my old one has. my new one does not have one.

ripley

Because the one you bought is a Timbo's APPS... You might want to go here for more details on calibration...

http://forum.mopar1973man.com/showthread.php/1527-Timbo-APPS

http://forum.mopar1973man.com/attachment.php?attachmentid=698

[dripley]

well i'll be.

ripley

---------- Post added at 12:43 PM ---------- Previous post was at 11:31 AM ----------

my voltage resd .607. i turned the screw on the bell crank till the voltage rose and backed the screw off and the voltage never dropped below .607 no matter how far i turned it. my target was .595. ibacked the screw about two turns past .607 and no change. ican move the linkage that liitle bitn with my hand and the voltage does not change until it reaches the origanal position, then it starts to climb. should the voltage have not dropped more?

[Mopar1973Man]

There is no target voltage on the new sensor just turn the screw till the voltage start to rise then back off to it returns then back off additional 1/2 turn. Thats it... No voltage to adjust to...

To clear this up more... (The best I can)

The fact is that the stock APPS sensor is a rheostat yes. But it is set at a particual voltage to the electronic switch inside reports to the ECM if it at IDLE or THROTTLING. If the voltage rises above the voltage set on the tag the switch changes to THROTTLING. Then when the voltage drops BELOW this voltage on the tag then the ECM switches to IDLING. This means the APPS voltage is disregarded and idling software takes over.

NOW... The Timbo APPS... There is no set voltage tag because the switch for ON IDLE and THROTTLING is mechanical this means once the bellcrank gets to a particual angle THROTTLING starts regardless of voltage. So there is no voltage to adjust it just a matter of taking the slack out of the bellcrank.

So now you know why you DON'T set for EXACTLY the tag voltage because now it will constantly flip back and forth between IDLING and THROTTLING causing issues with exhaust brakes, high idle software, etc.

It not about the voltage its about the fact of the Idle Validation switch state...

[Jwirth]

THANK YOU! THANK YOU! THANK YOU!,  

I kept looking at the instructions and all the internet voodoo and thinking that it made little sense. 
I had installed a Wells APPS and it resolved the original problem, lose of power and surging, but I traded it for a new problem, dead peddle.
When I first installed the APPS, the idle was 1100 and a reference voltage of .38 key on or off.
(Wells instructions says the voltage should be .5 to .6 volts.)
After reading your article I remounted the APPS and checked for free travel an disconnected the batteries for 1/2 hour +.
I reconnected the batteries and reference voltage on #3 with key off was 0 volts.
Key on the reference voltage on pin 3  read .55 volts. 
I cycled the accelerator peddle one time with key on, started the engine, and it idled 800 RPM.
Test drove it with no dead peddle incidents. 
If you would shave I would kiss you!

[Mopar1973Man]

20 hours ago, Jwirth said:

If you would shave I would kiss you!

 

Sorry I'm taken... 

 

The whole APPS sensor is misunderstood for my years. The voltage has ZERO to do with the PCM or ECM. Only the APPS sensor itself to control the IVS switches that all. 

[Jwirth]

So what's your take on cutting wire #23 on the PCM and running a jumper wire from the APPS to the PCM to bypass the ECM?

[Mopar1973Man]

29 minutes ago, Jwirth said:

So what's your take on cutting wire #23 on the PCM and running a jumper wire from the APPS to the PCM to bypass the ECM?

 

Bad idea. No need for the any wire mods.

[Jwirth]

17 minutes ago, Mopar1973Man said:

 

Bad idea. No need for the any wire mods.

You keep making me want to kiss you.
Someone had made the ATS modification to mine, so I unmodified it.  
I did keep the jumper from the APPS to the battery ground at the body. I figured adding an additional ground could not hurt. I also sanded the ground...again... which I suspect was the true cure for my torque converter lock problem. 
After a year of chasing the problem it is fixed and I love my Cummins again. I could kiss it. 

[Mopar1973Man]

Need two mods...

 

This one fixes the AC noise problem completely.

 

This protects the PCM from shorts on the blue field lead.

 

[wil440]

Just to add..... PO of my truck fitted a $15 APPS from china, I bought the truck with check engine light on. Turned out apps was no where near any required voltages and no amount of adjustment fixed it. It was less than a month old. Now in the glovebox as a spare get me home as truck ran in a fashion

[Mopar1973Man]

There is no set voltage for an APPS...

 

Stock or logic IVS APPS required voltage for setting the IVS switch state. That's all. Timbo's APPS uses the angle of the bell crank to set the IVS state. Where a logic APPS like stock will use voltage to state if its idle or throttling state.

 

 

 

Edited October 15, 2019 by Mopar1973Man

[dripley]

I have one of those my self. It works but with a constant 222 code.

[wil440]

2 minutes ago, dripley said:

I have one of those my self. It works but with a constant 222 code.

Great for a spare but thats all.... ? was one of the reasons truck was for sale, well that, CTM problems, seatbelt problems, electric window problems...... just the usual  

[dripley]

6 minutes ago, wil440 said:

Great for a spare but thats all.... ? was one of the reasons truck was for sale, well that, CTM problems, seatbelt problems, electric window problems...... just the usual  

Mine was surging so I tried the cheap one. It fixxed the surging so I bought another Timbo. It went back to surging with the new one. Turned out to be a wiring issue. Sure thought I was smart to buy the cheap one.