OK, I am loosing whatever hair I have left now...... Truck was giving me an intermittent dead pedal for about two months. Codes were P0121 and P1689.... got worse and worse until I had no pedal at all and had to idle my way half way home, until I thought to try the cruise control. Once I got downhill enough to hit 35 MPH in 6th at idle, I could set the cruise, and bingo, perfect. COuld use the accelerate button on the steering wheel and drove the rest of the way home on the highway A ok at 65 MPH.

So, I figure, this is easy, its a no brainer, the APPS. So $422 later, with a brand new APPS installed, and the APPS reset procedure done so many times I cant even recall, I still have a deal pedal. BUT the thing works perfectly on cruise controll !!@!!!!#@@@!!!!!

I checked the wiring from the APPS to the ECM, perfect. I checked the APPS voltage span, as well as the idle validation circuit.,.. perfect.

I AM LOOSING MY MIND HERE><>>>>>>...... And the cummins people, and the dealer are trying to tell me its the VP44... How the hell can it be the VP44 when the truck will run all day long on cruise controll but not with the pedal?????????

Does the PCM somehow talk differently to the ECM for cruise control than the APPS talks to the ECM, such that it runs on cruise but not on pedal ??? I cant help but think right now, that the ECM is not correctly reading the idle validation inputs from the APPS (the APPS is properly doing the idle validation, I am saying the input channels in the ECM may be bad).....

Man oh man am I furious. I have never been so aggravated troubleshooting a vehicle problem in my life........
Really makes me want to get a nice P pumped 12v with NO COMPUTER.......

Anybody have any thoughts on this?????


Kp

 

I am not trying to argrevate you further, so stupid suggestion #1 is:

You checked the throttle cable connected to the diesel peddle all OK?

Jim

 

The 1689 code tells me that the Pump is more your problem than the apps ever was.

Not saying the APPS is guilt free. But the 1689 is a communication error between the pump and the ecm. Usually caused within the pump circuitry, not the ECM.

You can check the connections on the back end of the pump for loose or corroded contacts, but there is a good chance that you are about to replace the VP44 as well.

On edit. I see you have an EZ on there. Disconnect it, and see what happens. This could solve your problems entirely. Report back on what you find

 

Lol... yes of course that is fine.... that would have been pretty funny eh??

 

I hear where you are coming from about the 1689 code and the pump. But I still cant reconcile how it works like a charm on cruise control.... any speed, any loading, perfect. Obviously the ECM is talking perfectly to the pump to drive any speed on cruise control without so much as a hicup....

Yes, the EZ and also the TST have been removed for troubleshooting purposes.....


Does anyone have information on how the cruise circuit differs from the pedal circuit in the ECM/PCM ??? I assume the cruise function is being performed in the PCM, and then that signal is sent to the ECM, which then sends signals to the pump.....

 

I thought the cruise was hooked to the same place as the pedal and used the Vacuum to pull the cable.

 

You might want to send qzilla a PM about this thread, he's pretty knowledgeable with regards to the electronic side of things.

 

No, on an 01 the cruise is totally electronic, no vacuum pot or anything like that....

 

Thanks for the tip.... I'll give him a ring....

He is the gent who makes his own boxes right ?? the adrenaline, right ??

 

My truck had no thottle respose at all once. Had the 0121 code thought it was the apps, so i changed it with dads and didnt help. Ran it down with a snap-on code reader and turned out to be a bad ECM. Hohn had the same problem around a year ago.

 

Yep, right now that is where I am leaning....

interesting thing is that I lost my oil pressure indication about a month ago as well. Pressure is fine, just indication.. I assumed it was the sending unit...but maybe the ECM's inputs are dying one at a time.... I am going to pull the sending unit right now and bench check it. If it checks out, I feel really good its the ecm.....

 

Mine turned out the be a bad ECM, as Blackie posted.

Only 18 months later, I got to replace the APPS for real.

Kev, I hate to say it but you might have to go one by one on the ECM pinouts and compare inputs to outputs.

To you have a voltage generator or a test stand of some kind?

The Cruise and the APPS use totally different parts of the ECM, so I'd suspect the ECM. It's the only thing that makes sense at this point. I'm sure I could be missing something, though.

hmm.

 

well I think the oil pressure sending unit is indeed bad. I assume its a resistance device, correct? I dont see any resistance change over any of the pins as I apply pressure to it on the bench....

was really hoping that would point to another bad input in the ECM, but looks like not.


Yeah Hohn and black I'm really thinking its the ECM.
By the way, does anyone else think its not the greatest idea to mount a printed circuit board device on the side of a diesel engine block ??? Can you say vibrations and heat ??????




ANybody got any 01.5 ECM's lying around I can rent to troubleshoot with ????


KP

 

Contact Bob Wagner.

 

This may be a long shot but before you spend any more money check the voltage at the APPS. You mentioned the oil pressure sender is not working and now the new APPS is not. The common thread is that the ECM generates 5 volt power for all the senders and if it is missing from the APPS and oil pressure sender it will cause what you are experiencing. I do not have my shop manual handy but find the pin on the APPS or oil pressure sender that has 5 volts and test to be sure it is there.

By the way, the oil pressure sender is not a variable resistance, but a solid-state chip. It is not easy to test without powering it up and then checking for the output.