VP44 or ECM issue?

torque beast

torque beast

addicted to diesel
Joined
Feb 21, 2008
Messages
148
So I have a 98.5 2500 Cummins with auto trans. It has always fired right up and idles great. Every now and then it would hesitate when starting from a dead stop especially if going uphill but would still run decent. Then my wait to start light quit coming on immediately and had a several second delay so I sent ECM off to be reburbished and when I got it back the wait to start light comes on immediately but now have an ABS and Brake light on and truck will not run right. It starts and idles great and will rev to 3200 in park easily but if I put in gear with foot on the brake it has no power and will not go above 1400. If I try to drive it it is like in limp mode unless I floor it then it will gradually kick in like a two stroke engine and go. My gut says the ECM is screwed up still but with having some hesitation before it could be vp44. I have done the ground mod, new coolant sensor, new map sensor, new apps sensor and verified it is set correctly. Is there a way to bypass ECM and control the VP44 to troubleshoot the issue?
 
The ECM has nothing to do with the ABS or brakes. I’d say you have another issue there. Cummins has a tool for testing that bypasses the ECM. I don’t remember what it’s called or where you’d get one. Some scanners offer injector cut and cylinder contribution utilities.
 
That is what’s weird because I never had the lights until I had the ECM refurbished
 
Are we talking ECM, mounted on the side of the engine above the starter, or the PCM, on the passenger side of the firewall?
 
torque beast said:
Is there a way to bypass ECM and control the VP44 to troubleshoot the issue?
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Yes, there is. Trent at what once was Outlaw Diesel, now Titanium Diesel, in Blackwell, Ok has a box he plugs onto the VP44. He can start and run and test the IP controlling it with the box and rule out an ECM failure. When my truck started doing this crap, it was the Vp44. Your might not but I'm placing my bets on the IP. Good luck.
 
If it turns out to be the vp44 is there a certain one that uses more robust parts to avoid the common failure points?
 
So I got to thinking and it seemed to me it acted liked a boost leak so I checked and could not find one. Then checked voltage at the brand new map sensor and it shows 5v and a good ground but when I back probe the signal wire it shows 5v as well and does not change. I even took out and used 20 psi of air on sensor while plugged in and no change. Am I right thinking the signal wire should be 4.5v at idle and go down with boost?
 
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torque beast said:
So I got to thinking and it seemed to me it acted liked a boost leak so I checked and could not find one. Then checked voltage at the brand new map sensor and it shows 5v and a good ground but when I back probe the signal wire it shows 5v as well and does not change. I even took out and used 20 psi of air on sensor while plugged in and no change. Am I right thinking the signal wire should be 4.5v at idle and go down with boost?
Click to expand...
Check your ground with key off and again with key on. I had a truck that the grounds would disappear with key on..
 
replaced the map lately? there are diff wiring pigtails...i chased it all summer one time cuz i replaced the map and got the wrong yr pigtail with the new sensor...that 5v bullshiz will drive ya insane. the pigtail has 2 wires that are in diff spots and it will fk up the grounding
 
Yes it had a new map sensor but I removed Diablo puck and went through everything again. Found a boost leak in wastegate pod so pulled hose off and plugged it. Found new map sensor showing .42v key on and found data that says ECM is looking for a minimum of .50 so I checked my old map sensor and sure enough it showed .50 and was operating correctly so I put it back in and now truck runs fine.
 
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