Output Speed Sensor pins 44 and 45 (C2) Voltage

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Junior Member
Feb 12, 2024
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Ram Year
5.9L Turbo Dsl
What is the correct voltage for the output speed sensor pins 44 and 45 (C2)?

I'll post all the history below, but the original ECM in my truck, a 2004 Dodge RAM 2500 3/4 ton 4WD (6 Cylinders C 5.9L Turbo Dsl OHV 359 CID), was damaged so I bought a new one. The truck runs fine but is throwing a lot of error codes (below). My mechanic did a bunch of diagnostics and said P0720 is the important error code. According to my mechanic the voltage on the pins to and from the output speed sensor are incorrect, one should be 5v and the other 0v since one sends out a signal, the other receives a signal back. The ECM is putting out 2.5v on each pin. Flagship One, who I bought the ECM from, says 2.5v on each is correct. I had my mechanic talk to Flagship One, and both are positive they are correct. I'm not sure who to "push" on, so who is correct?

The back story for those who want more details.

I purchased the vehicle from my sister since she wasn't driving it very much. Mainly around town once in a while just to keep it running. 2004 with 150,000 miles on it. Prior to purchase she had her mechanic go over it to make sure there wasn't anything that should be fixed and he gave it a clean "bill of health". In retrospect I suspect he missed the issue, because it wasn't that severe with limited driving. Drove it home, 14 hour trip stopping only for fuel, with no problems. Once home drove it 3 or 4 short trips, 20-60 miles each with multiple stops, including taking it to the SMOG shop so I could get it registered in California. Passed SMOG without issue.

Tried to start it one day, it would turn over but would not start. Also, most of the gauges on the dash were not working. The only error code was P2509.

Had a friend who is a former tank mechanic come out, and he eventually diagnosed the problem as the ECM. 3.5 years ago my sister's mechanic changed the fuel pump, and did not get the fuel line reattached correctly, so it was spraying a very fine mist of diesel all over the inside of the engine when the truck was running. Probably during the drive to my house, when it was prolonged, it soaked the interior of the engine around the fuel pump. It was dripping out of the bolt holes for the ECM. It also corroded other parts in that area, including the coating on the ECM and wires on the front wiring harness around the ECM plug.

I purchased a replacement ECM and new fuel line and he installed them. The truck starts and runs, no misfires, stalls, etc., but throws numerous error codes. His code reader was also unable to read the VIN number from the ECM, it came back as all Q's. The codes were P0148, P2122, P0118, P0113, P2509, P0193, P0336. Tried to clear the codes with the reader, all but 4 would clear, but as soon as the truck was turned on again, all the codes would come right back.

Filled out an RMA and sent the ECM back to Flagship One. They re-flashed it and shipped it back. Installed the ECM again, same problems with numerous error codes even though the truck seems to run fine. Codes now are P0073, P0517, P2122, P0118, P0113, P2509, P0193, P0336, P0720. At that point the code reader has the right VIN number in the history area, but when asked to read the VIN it still couldn't. It came back Q's or blank. Also the emergency brake light and ABS lights lit up on the dashboard and would not go out regardless of what was done.

Ordered a pigtail for the front wiring harness, which had a fair amount of damage to the coating on the wires, and my friend installed it. The code reader can now read the VIN number correctly from the ECM, and the e-brake and ABS lights are working as expected. Once again the truck drives fine, up and down hills, accelerating up to 65 mph, etc. Only drove it a few miles though as I'm concerned about either doing damage, or it dying on me. Still has the long list of error codes. All the gauges on the dashboard are working correctly.

My friend is only available on the occasional weekend, so I finally took the truck to my normal mechanic. And that's where we are now.