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The root issue I am having is I am getting the APPS low voltage code.  How I realized there was an issue is my BD exhaust brake intermittently will not work at low rpms (and it changes minute to minute what rpm it will cut out at, but usually around 1000 rpms).  I checked codes through my Edge Insight and got the APPS low voltage code.  So right now, I am leaning towards thinking it is alternator related, but my initial quick test in the parking lot at work doesn't agree with that.  I'm going to break up my post into each little point, otherwise I ramble on a long confusing paragraph.

 

Previously, my exhaust brake acted up my batteries tested as being poor to marginal, so I replaced them and my exhaust brake acted completely normal again up until now (I believe that was last summer).

 

AC noise check came in at .022 VAC.  I don't know if I believe this though.  I had everything turned off (stereo, lights etc) but I didn't unplug the fuse to my A-pillar gauge set or my exhaust brake (but the switch was turned off so I don't think this would be an issue).  Also, my multimeter is a hobbyist one: a fluke 17b+ which is an asian market unit, not a solid unit like a fluke 87, and it doesn't read true RMS so my understanding is these readings won't be true.  Can this be confirmed?  Do I need to get someone with a better unit to test the AC noise?  Did I have enough accessories turned off?

 

Alternator voltage came in at 13.7-13.8 at idle.  Before turning on the truck battery voltage was 12.71 (Batteries are about a year old and are high quality batteries).

 

Exhaust brake ties into the idle verification system and then I had to manually set the sensitivity on the controller so when I push on the accelerator the exhaust brake kicks off.  I guess I should check this connection, because it could be poor I guess?

 

The records from the previous owner (My wife's uncle who passed away) show that the APPS was replaced around 7  years ago or so.  Maybe another one bites the dust?  I haven't had a chance to find it again but I think I found a detailed flow chart on here somewhere to diagnose APPS.  My understanding is I can try to manually put the APPS back into its stock voltage range and the results seem mixed by doing this?  Obviously if APPS is bad, purchase and put in a Timbo APPS?

 

Hopefully its not the PCM?  I understand they are very expensive and hard to find and sometimes don't even transfer well to a different truck?

 

What's my next move, attempt to diagnose the APPS and/or re calibrate the voltage?

 

Thanks as always!

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From your post I don't believe you have a DC supply problem. New batteries with a resting voltage of 12.7 is a sign of good health...I'm assuming the test was performed individually to show a resting voltage in the 12.7 range? Also, your idle charge rate appears to be well with in range of a pair of parallel storage batteries. 

 

As for your Fluke...many DVM's (digital volt meters) will display AC on a DC source or rail however;  the accuracy of the peak to peak AC component may not be exactly accurate but, for the most part, it provides an indication close enough to know if you have a leaky diode in the rectification pack that causes ripple to be over acceptable levels. I would not be concerned about having a "True" RMS (root means square) DVM in this application. This reading (RMS) is a mathematical derivative of taking the peak to peak AC value (easily viewed on an oscilloscope) and then multiplying that by .707 to obtain the RMS value. Hence, 1 volt x .707 =  .707 volts AC RMS value...it's not important to us in this scenario of analysis. We are concerned with stable clean DC consistency through our entire system.

 

I would examine the physical aspect of the exhaust break itself and a quick re-calibration of the APPS device to set it's bottom end level or resting point and see if this eliminates the inconsistent operation of the exhaust valve. I also assume, the operation of this exhaust break worked in a normal fashion for a period of time under your present ownership?

 

Cheers,

W-T 

   

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7 hours ago, Timburrr said:

if APPS is bad, purchase and put in a Timbo APPS?

 

I replaced my APPS with a Timbo (my truck has a manual transmission) and I seem to recall that there was a note about the Timbo not having an idle validation switch to control additional after-market devices, such as an exhaust brake.  I don't know this for sure, but it is something that you may want to check out.

 

- John

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I have Timbo and exhaust and they work fine. When I was having surging issues it would disable the E brake with any surge no matter how small. 

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Same here I got a Timbo's APPS and Jacobs Exhaust Brake. As soon as the IVS is ground on the idle side then the ECM counts 2 seconds then enables the exhaust brake. I've got a second switch on my transmission stick that allow me to arm instantly on the exhaust brake. 

 

 

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Thanks guys. Sorry for the late reply and thank yous on this. Went out of town to see the wife's family for the weekend and we all got sick. 

 

I understand the exhaust brake is activated by the IVS but my understanding is the IVS is triggered as recognizing being in idle based on APPS reading. I've noticed my APPS will jump around, sometimes as much as maybe 10%. Not always but a bit. If I'm idling it will periodically blip to 4, 5 maybe up to 8% for an instant between mostly resting at 0%. 

 

Also, my alternator reading on my edge bounces between 13.6 and 14.0 but is usually 13.8/13.9.

 

Since previously the problem was fixed with my new batteries it seemed logical to me that it was alternator related. 

 

First step will be as recommended try to reset the APPS voltage. If not I will either go through the APPS problem solving steps or just put a Timbo APPS in? Can I confirm my exhaust brake will work with it?

 

Thanks again fellas

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46 minutes ago, Timburrr said:

but my understanding is the IVS is triggered as recognizing being in idle based on APPS reading.

 

On the Stock APPS it is based on voltage in must fall below the tag voltage at least 0.1 below.  On Timbo's its based on bellcrank angle, no voltage used. 

 

47 minutes ago, Timburrr said:

First step will be as recommended try to reset the APPS voltage.

 

Just replace it with Timbo's. The voltage should NOT be adjusted on a Stock APPS

 

48 minutes ago, Timburrr said:

or just put a Timbo APPS in?

 

Absolutely. 

 

48 minutes ago, Timburrr said:

Can I confirm my exhaust brake will work with it?

 

Been running Timbo's on my exhaust brake for over 7 years now. No issues. 

 

Compare...

 

Stock APPS and the IVS circuit.

plateoffup8.jpg.ecff05881a4a7e19848bca29

 

Then Timbo's APPS without any electronics. 

Image result for timbo apps

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And..... the dealer wants 500 smackers for that factory Apps. :cookoo:. And.... that was the price 10 years ago.

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21 minutes ago, JAG1 said:

And..... the dealer wants 500 smackers for that factory Apps. :cookoo:. And.... that was the price 10 years ago.

Never did understand why you dould not just buy the sensor alone instead the sensor and bell crank assembly. 

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Posted (edited)

I figured it out long ago,  most dealers are retarded, especially the ones selling parts. Bunch of zombies. They couldn't find their own dikk with a compass and a flashlight. 

Edited by Dieselfuture
Dumb phone
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Some need the use of a microscope if they know the general area.

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I have had the Timbo APPS in my glove box for a couple weeks here and hoping to have time to get in later this week.  Thanks everyone!

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