24v ECM or VP troubles

Ridemywideglide

Ridemywideglide

Diesel NON-Pro
Joined
Aug 13, 2006
Messages
369
Working on a 24v for a customer, even tho I'm not a diesel shop, I do have some experience with the 12v's that I've owned.

Customer decided APPS was out, quick scan showed P0122, so he ordered a APPS from Geno's. put it in and it's the same issue.

Starts fine, no throttle response. If I put the pedal anywhere other than idle, then it will rev slowly, uncontrollably, until you let off the pedal. Good settings on APPS, but scanner only shows voltage "at tps" until I start the truck, then it shows zero. When cold I can get a couple seconds of pedal response then it goes back to the same crap.

Wondering if this is a sure sign of ECM failure, or there are other tests I need to do on the VP the help narrow this down.

Thanks
Brad
 
What year truck? That is usually the sign of a vp44 failure
 
Buddy is working on one that's doing the same thing. New pump and apps, also. I figured it was the ECM.
 
Can you borrow an ECM to check??? I'm thinking VP, but I have seen a lot of wonky ECM issues as of late.
 
Sorry I didn't include that info, it's a 2002 6 speed. Looks like he will be even more unhappy with this news.

Unfortunately I don't have a swap ECM, and no salvage yards near here have one available.
 
2002 ecm's are weak at best. find a good used 2000 or 2001 and I can flash it for the 2002. You will be ahead of the game if its the ecm.
 
My vp did this when it went out. Exact same problems.. Even went and put a new apps on it also. But I could be wrong..


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Bad VP is your problem. I got and ECM you could try but unfortunately I'm in Denver.
 
Try running it with out the ECM. Put power to pin 7 and ground to pin 6 at the VP and start it. While running put ground to pin 4. If it revs up normally then its possibly an ECM issue. Also check all the wiring to the APPS. Make sure you have 5 volts coming into it.
 
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Jeep, when hotwiring it like that there is no way to rev it up, as there is no connection from the APPS/ECM. It is just a check to see if it will start.

Ed
 
mine did the same thing on my 99 the module on top of the pump was bad luckly I worked for dodge at the time and was able to figure it out without dumping a lot of money if you know some one with a star scan from dodge and it doesn't communicate with the vp pump then the control module is bad
 
jeepxj97, it will start and run just fine, just no throttle.

So after talking with the customer yesterday, it seems the lift pump and VP were replaced about 6 months ago, with parts from dodge dealer, installed by a 3rd party mechanic shop...

Dodge has told the customer they will swap out the VP for a new one, but I need to be sure this will fix the problem.

I have a "flow chart" of sorts I found on the internet that right off the bat asks me if the code is set by ECM or JTEC...?? My genisys 5 scanner gives me a choice of engine diag, either cummins or jtec, and both now show a p0122 and a p0123 code, with the Cummins choice showing an additional code p0236 for MAP sensor.

How do I determine which computer is setting this code? It seems more unlikely that the VP should have a problem since it is recently new. Less than 12k on it since install. Or is this a typical scenario with a dodge replacement pump?

And I know no one with a star scan. Maxtorq, I may be interested in working something out with you to "borrow" you used ecm to test this out. Tossing you some coin and paying shipping to know for sure would be way better than blowing all this labor on a part that may not be the problem.

And it doesn't look like I stated this previously, but the Tach ALWAYS works, never intermittent or dropped.

Thanks
Brad
 
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And if I go through the "Engine JTEC" side of the genisys software, I can track the apps voltage while it's running, but it only shows 3.89v at full throttle. On the "Engine Cummins" side of the scanner, I will see the same voltage from the apps until the truck starts, then it drops to zero voltage no matter where the pedal is.....
 
I'd say you are on track. I had same symptoms in basically same truck and it was an ecm.
 
i had the same problem with my 99, but the ground was junk, so i supplied a seperate ground from the apps straight to the battery. works pissers now.
 
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