Engine/Transmission (1998.5 - 2002) Throttle Response through the APPS

[480RUGER]

I NEED SOME HELP. What causes a slow voltage rise from the APPS to the computer? I checked four other CTD 99-02 with a scantool and when I gave them full throttle the voltage instantly goes up.



Now on my 2K when I do the same thing I can watch the voltage rise in several steps. It will reach the same peak voltage just take a few seconds. I tried two other new APPS on the truck with the same result. What could cause the delay? What does the signal go through that I can change? I have full top end power just the throttle is slow to react which causes more smoke at take off and when I try to down shift on the interstate it just lags till the voltage rises and off I go.



The Smarty helped but not like it does on most other trucks. I don’t have any codes. I changed the MAP and IAT sensors. FASS has a new filter. I was thinking about the Draw Straw but from the looks of the smoke I don’t have a fuel problem. I’m ready for twins and 6s just wanted to get this fixed before I went any farther.



Thanks in advance.

 

[480RUGER]

Bueller, Bueller,... . Anyone, Anyone,... . Anyone?

 

[ROADWARRIOR]

Have you tried calling Cummins tech support?

 

[paulb]

I would start by checking the voltage at the APPS. The one I would be most concerned about is the signal ground, but I would check them all. If they are okay at the APPS, then check them again at the ECM. I would also check the voltage that you see at the APPS with what the scan tool displays.



Paul

 

[480RUGER]

The voltage matches my truck at the APPS and the ScanTool with all the other trucks and with the new APPS on mine. All other trucks go to full output voltage instantly while mine just counts up slowly to peak output voltage on the ScanTool.



When it goes IT GOES! It just takes a few seconds to act on it.

 

[paulb]

The voltage matches my truck at the APPS and the ScanTool with all the other trucks and with the new APPS on mine. All other trucks go to full output voltage instantly while mine just counts up slowly to peak output voltage on the ScanTool.



When it goes IT GOES! It just takes a few seconds to act on it.

Let me make sure I understand. If you measure the voltage at the APPS with a volt meter(not using the scan tool), it goes up slower then the rate that you move the throttle?



Paul

 

[480RUGER]

No. The DMM voltage at the APPS goes along with the throttle. Voltage from 0% position to WOT is instantaneous like it should be. It was with the ScanTool on my truck only that you can watch the voltage rise in steps. All the other trucks we tried had no hesitation.

 

[480RUGER]

Any other Ideas?

 

[obert]

Was there a diff in ecm software version between your truck and others? maybe it was just a communication quirk between your ECM and the scan tool. That would explain the electrical issue. Lots of smoke and slow engine response makes me think your turbo might not be the perfect fit, like maybe the impeller side (hot side) is too big and not spooling fast enough to handle the fuel going into the engine... ... .

 

[480RUGER]

I don't think so. It's a HTT Street Stock HTB2 62mm/12cm HX-40 Exh Hsg. As far as I know this is the smallest HTB2 they make. Thanks for the input but I still think it has to do with the signal from the APPS to the ECM. I just don't know what would cause the slow ramp up of voltage.

 

[480RUGER]

I'm running the truck back to Olee next week. He has all my goodies on the bench waiting for a truck to put them on. Once the truck gets going everything is great. I just can’t get the jump on someone quick.



I went through the service manual and didn't see anything inline with the voltage signal. I hope it’s just a flash but I'm worried about not being able to go back to my old software if the updates act funny. I know several people with a newer flash and the truck ran worse. That was a few years ago so I don't know of any new issues.



Thanks for the input everyone. When I find something I’ll put it in a new post. Until then any other ideas would be great.

 

[480RUGER]

I checked all the grounds I could find and still the same problem exists. I haven’t done a new flash yet because I don’t think it will do any good. I’ve checked newer and older 2nd gen. trucks and they all work correctly. HELP!

 

[AFarmer]

Stop by Cummis off 85 while you're up here and get a new APPS.

 

[ERuhl]

Stop by Cummis off 85 while you're up here and get a new APPS.

Why would that behave any different from the two new ones he's tried? Note the APPS is performing as expected:

The DMM voltage at the APPS goes along with the throttle. Voltage from 0% position to WOT is instantaneous like it should be.

I tried two other new APPS on the truck with the same result.

Are you certain the delay is real? You mention excess smoke when you take off, but a slow throttle would produce less smoke not more. Is it possible the issue is only on the bus communication with the scan tool? Have you tried a different ECM?

 

[480RUGER]

I don't have the smoke now like I did. I think it was from the Mach3s. I hardly have any now with the Mach6s and twins (at take off). I DO still have a very slow response while trying to pass. Like I said once it gets going all works great.



As you noticed I did try a new APPS and it acted the same. I’ll keep looking and if I can get my hands on another ECM I’ll stick it in and see what it does. I don’t know what else it could be.

 

[480RUGER]

Anyone ever have an auto transmission causing these symptoms?



I know I adjusted the APPS voltage just a little on the high side from what Bill @ DTT said it should be but only by a couple of tenths. Where does the Scan tool get its reading for its throttle voltage? It’s much less then at the APPS (around 2V lower) but exactly the same on my truck as all the others I checked. This is where I was reading the slow ramp-up of my voltage, not at the APPS.