Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Working on a 2007 Dodge Ram 2500 6.7 with a no crank/no start condition. No engine codes, but I do have Central Gateway Module codes that lost communication with PCM and ABS. I can communicate with all of these modules using the Autel Ultra. I have no square wave with my o-scope, I only have a 2.5vdc bias voltage. Also, the PRNDL is not showing on the dash, however I do have power to the IC and lighting. Any help is greatly appreciated.
BLEE wrote: I have no square wave with my o-scope, I only have a 2.5vdc bias voltage.
Was that 6 & 14 at the DLC? That truck probably has a diagnostic CAN which is a straight shot from the DLC to one module. That module acts as a gateway between scan tool and the vehicle networks. So unless you're testing with a breakout box and a scan tool connected you're not going to see any network traffic at the DLC.
Have you done any voltage drop testing with just a simple voltmeter? Im no expert but I did recently diagnose my cars no crank issue which ended up being worn out brushes in the starter.
If you've got access to the starter without disassembling a lot you could try jumping the starter straight from the battery. If (like in my case) you'd have to remove the whole intake manifold in order to get to the starter you could instead remove the starter relay and jump the connections there (bypassing the ignition and park/neutral switches).
Have you tried cranking while in neutral? That's a quick, easy way to rule out the P/N switch, which isn't likely to be the prob but IS possible & worth ruling out.
