How To Reset Ecm On 5.9 Cummins

[Manases Blakemore]

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I have a 98 2500 24v auto, and ever since I've owned the truck I've been having this issue but just never attempted to do anything about it until now. I've just rebuilt my transmission to hold 550hp, am looking to add a tuner but I know I should fix this before I try to add more power. I have read the forum here about adjusting the apps and numerous other forums and cannot find anything to specifically relate to my issue.

To start, my issue is that when I plug in my OBD scanner, my APPS sensor was reading 8.6% at idle and 71.3% at wide open throttle. So, after doing some reading, I attempted a reset. I unhooked the batteries, let the truck sit for about an hour with the key on, and then turned key off, hooked batteries up and continued with the reset process. I have done this multiple times and it seems to correct the readings on my scanner to 0% at idle and 100% at WOT for about one day, then it resets back to the 8.6% and 71.3%. I am pretty positive my OBD2 scanner is reading correctly, I plugged it into my friends truck whose is identical other than his being the 2000, and his read 0% at idle and 99% at WOT. His is also bone stock but appears to have much more power than mine.

Next, I tried adjusting the apps sensor using the method Mopar Man posted here in the forum. I am pretty positive my APPS sensor is stock. My idle voltage was .49v, and the back of my apps stated the voltage should be below .569v so I adjusted the apps to .54v at idle (note, I did not loosen the apps screws and rotate it, I used adjustment screws like what was recommended). I then adjusted the WOT voltage. It was reading 3.63v, and while I couldn't find an exact voltage anywhere, I found a YouTube video Mopar Man linked to the adjustment forum that said it should read around 3.8v, so I adjusted it to 3.8v. Also, I checked to be sure that the apps did not have any voltage spikes or drops throughout the travel, which it did not. It was a nice smooth climb from idle to WOT. Now, after the adjustment was completed, I checked my APPS reading on my scanner and it's now showing that my idle percentage is 10.2% and my WOT is 74.3%. I've tried resetting it a few times and continues to default back to the 10.2% and 74.3%.

I'm stumped. I've done all the research I can to try to figure this out without creating another post because I know there's thousands of them out there, but I cannot find anything that relates to my issue. Do I need to just replace my apps sensor or is something else wrong? Any ideas or suggestions would be greatly appreciated.

Yes, my wait to start light is delayed. About a year ago I replaced the ECM with a new one I got offline because the old one went bad. Caused my lift pump to quit working and took out my VP. Had my lift pump on a toggle switch for awhile until I ordered the ECM, replaced it and everything seemed to work great. I still had the delayed wait to start light even after replacing the ECM but not like before. Before, it was delayed about 10 seconds every time I turned the key. Now it comes on right away about 80% of the time and when it is delayed its about 1-2 seconds. Do you think my new ECM could be bad again? I did everything I could before installing it to try to ensure its longevity by replacing the alternator and rerouting the passenger ground wire getting the AC noise within tolerable limits.

It's just like SD cards and usb thumb drives they have limited cycles like 100K. So if the ECM stores data every few seconds or minutes it wears on it. Example updating the minutes in the engine hour counter.

To save yourself the money you can try and see if they warranty it or replace it. Cant speak on their behalf but we are the Top Rebuilders for these computers. Low voltage and dirty grounds are common problem for these ECM'S,

Yup I would send the ECM off to @Auto Computer Specialist and let them fix the ECM. Then I would suggest pulling you alternator have it bench tested for AC ripple. Then if you replace the alternator make sure to have the new one tested I've seen new in the box that are bad. Then I would go over to the article section and do the W-T ground wire mod. As for the APPS I would replace with a Timbo's APPS it has no voltage to set or electronics completely mechanical throttle sensor.

I have a friend who has a 98 24v, exact same truck as mine, same manufacture date and everything. His is P-Pumped, so he loaned me his ecm to plug into mine. I plugged it in and immedietly noticed it idled lower, had more power, and the APPS read 0-100% like it should. By the end of the day it was doing everything my old one was. Delayed wait to start, low power and APPS reading between 8.6-71%.

Do the W-T ground mod, like Mopar Man suggested, along with the Alternator and PCM protection mod and PCM Ground Splice Repair mod. Have the batteries tested, a weak battery can cause problems. I just did those mods on a customer's 1999 truck this weekend; it brought the AC voltage down from .05V to .025V, a 50% reduction.

The reason I asked if there's a way to identify the alternator is because when I purchased the truck two years ago it had two brand new batteries and a remanufactured alternator that had just been put on. The alternator does not have a sticker on it to identify the brand and I have no idea where it was purchased from. I'd hate to buy a rebuild kit for a denso alternator and end up having something else...

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