Bad Injector Ramps (Red Trace In This Image)

Jeff Owner/Technician Memphis, Tennessee Posted   Latest   Edited  
Case Study
Driveability
2007 Dodge Nitro SXT 3.7L (K) 4-spd (42RLE)
After Running A Few Seconds Sets All 6 Injector Circuit Codes. Pcm Has Been Replaced Twice
Tipm Has Been Replaced

Cylinders 2&3 have no Injector Pulse. I have unplugged the throttle body, Alternator and all injectors. Ramps start out better than this but not as I would expect to see them and then get worse after approx. 6 seconds till they look like the attached picture and follow video link. 

Injector supply voltage stays level and clean. The #1 injector scope pattern voltage looks normal. The circuits shown on the picture are Channel 1 is injector 1 voltage. Channel 2 is red trace and is injector current ramps. channel 3 is voltage feed to all injectors and PCM measured at fuse panel. Channel 4 is coil current ramps. I even switched current probes to see if one of my probes was damaged. They were identical patterns. Any Help on this vehicle will be most appreciated...

youtube​.​com/watch?v=h16NEe…

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Bruce Technician
Spring Hill, Tennessee
Bruce
 

Where do you have your current probe?

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Jeff Owner/Technician
Memphis, Tennessee
Jeff
 

All connections were at TIPM except 31 injector was at injector connector.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff
 

read a few cases of RFI from a coil doing crazy-azz juju on Chyrsler/Jeep. Try running it with one coil at a time disconnected.

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Eric Owner/Technician
Edgerton, Wisconsin
Eric
 

That is noise on the wire, and it appears that other hardware is powered by that circuit. Those spikes appear to be there KOEO. I took a quick look at the wiring diagram and found a capacitor on that circuit, I will guess it has failed or is disconnected or damaged. Locate and test it, or just replace it. There could also be a component on that circuit that is extra noisy and the capacitor has

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Robert Diagnostician
Ballston, New York
Robert
   

It appears you need to current ramp the injectors at the injector. There is noise from other circuits whre you are tapped in. Also power should be voltage drop tested at the injectors that are setting the codes. Also should scope for he ground switch at the injectors to see if it is switching correctly from the engine module. At first glance without being able too see your complete scope setup

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Jeff Owner/Technician
Memphis, Tennessee
Jeff
 

The pcm is setting all 6 injector circuit codes after it runs a few seconds. I will do the tests that you suggest tomorrow and let everyone know my results. I tried to upload the pico file, but it will not accept it. If you want a copy please send me an e-mail address.

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Cuba Mobile Technician
Phila, Pennsylvania
Cuba
   

How about setting up a google drive or Dropbox file, and posting the link here? It would make it easier for anyone to see it, either now or in the future. Make sure you make the link "visible to anyone who has it" setting. FIle you're trying to upload may be too big to post here.

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Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

That mess is not being mirrored in the voltage waveform so I would say that you are getting noise and/or other signals in your current waveform.

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Jeff Owner/Technician
Memphis, Tennessee
Jeff
 

Unfortunately this job is on hold due to Head gasket leak found during additional testing by tech on site. I will let everyone know when and if this job resumes.

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