Engine/Transmission (1998.5 - 2002) Help!!!! Recalabrated APPS and have 1300 RPM idle!

[EGaskamp]

I just got done recalibrating the APPS, It was at . 504 before calibration and set it to . 642 as it said on the back of the sensor. I started it back up and it idles at 1300 RPM's. What did I do wrong?? I thought you were supposed to set it to what ever it said on the tag. The CRAPPY torx head is about to start to strip out. Please help!!!



Eric

 

[Rebel Ram]

Is your voltage still right? If so leave it alone for a day or so. Mine did the same thing and then settled down.

 

[EGaskamp]

Ok, that makes me feel a little better. I haven't checked the voltage yet. How long did you let your truck sit? Did you unhook the batterys? I need the truck tomorrow, thats why I'm wondering. I hope it calms down. Thanks for the quick response. I'll let yall know how it goes.



Eric

 

[EGaskamp]

I just went out there and started the truck and everything is running perfect. It seems to idle smoother. It may just be all in my head though! Thanks for the help.



Eric

 

[PC12Driver]

If I'm reading the directions correctly that are floating around here on how to "reset" the APPS, it seems that the only thing that is being accomplished is re-clocking the APPS potentiometer. If the engine idles where it should and reaches redline RPM somewhere near the floor, why adjust it? With our 24v engines, voltage from the APPS is proportional to RPM. If the truck was idling properly at . 504v, and you cranked it up to . 642, of course it will idle higher. Not to be mean, but I think you went wrong by adjusting something that didn't need to be adjusted. What were you trying to fix?

 

[EGaskamp]

Well, I had the "dead pedal" a few times. And from what I've heard the proper votage is what it says on that tag on the back of the APPS. It was a little low, so thats why I recalibrated it.

 

[Walt-L]

Recalibration of the Apps to match the 23 pin in the PCM is primarily for the transmission. This keeps the engine speeds in sink with the Auto trans. When I reset my APPS, The truck ran like SH**!! I put in a new IAT sensor and bingo... The Truck ran noticably better than before. Before the reset, I never would have known the IAT was shot. I had installed the DTT wire filter to get the trans to stop hopping in and out of OD and did the recalibration as recomended in the instructions from DTT. This fixed about 70 percent of the OD problem. I since have read that one should make a direct battery ground wire spliced into the APPS ground wire that comes out of the APPS. The claim is the ECM ground pin is too fine a ground connection for the APPS. Does anyone know the color of that APPS ground wire? I seem to have missed placed that info.

 

[PC12Driver]

Okay, the auto trans thing makes sense to me. That way the PCM (controlling the auto) is on the same page as the ECM (controlling the engine).



I am curious as to what the rationale is for the re-clocking of the APPS is to fix the dead pedal syndrome. When you look inside an APPS and see what is accomplished by the latest and greatest set of APPS "recalibration" directions, it would have nothing to do with the dead pedal or surging symptoms. Since the ECM will re-learn the new high and low voltages from the APPS the first time the accelerator pedal is pressed to the floor and released after turning the key on once the batteries are reconnected (per the service manual), you're pretty much right back to where you started. Walt's auto transmission explanation would justify the adjustment, though.



There are two different methods of "recalibrating" the APPS floating around on the TDR, and I think the purpose of each one has been blurred. The first (disconnect/reconnect the batteries, key on, depress/release the throttle) will "teach" the ECM the voltage range of the APPS. The second (the newly discovered re-clocking method), as Walt has pointed out, will sync the PCM and ECM throttle readings to make the auto transmission shift correctly. The first method may fix a dead pedal (if the ECM completely forgot the voltage range of the APPS), and the second method has nothing to do with those symptoms.



Of course, if I'm missing something, someone please fill me in. But, imo, it seems that this new method of re-clocking the APPS is pointless unless you're trying to fix a shifting problem in an auto.

 

[nps]

Of course, if I'm missing something, someone please fill me in. But, imo, it seems that this new method of re-clocking the APPS is pointless unless you're trying to fix a shifting problem in an auto.

Agreed. And because the new procedure came from DTT, even makes more sense that it is tied to auto transmission problems.



Think the poster's original high idle problem is the same that I pointed out on another thread sometime back - the DTT procedures do not include the step on unhooking the batteries and relearning the idle voltage.