So I replaced my ‘04 Ram gas with a ‘03 Ram diesel. Have had the truck for a few months and all of a sudden I am getting erratic throttle, check engine light and dead pedal. I have pulled the code and got P2121. First time it happened, it had P2121 and P2123. These issues seem to be linked to the ACCS sensor.

Here is the scenario I have. Start the truck and it runs fine for 4 or 5 miles then acts up. I have a Smarty tuner that came with the truck so I plugged it in and found the code, cleared the code and updated the ECM with the stock tune. Truck runs perfect afterwards with no issues until it sits for a day or so and then I get the same thing.

Something I noticed is the voltmeter after startup stays below center for several minutes and then climbs past 14 and stays there. During the initial timeframe, the lights flicker and then they are fine.

New to diesels so any help would be appreciated.

Thanks!!

 

Will your tuner read pedal position, and throttle position values? If so, next time it screws up, see which value is out of range.

 

Thanks Hey You for responding!! I couldn’t find anything in the tuner that indicates pedal position but will look into the tuner specs further and see. It came with the truck and I have no user manual so will try and get one.


My Son talked to a few friends that work on diesels and they said this generation of Dodge diesels were known for wiring harness issues especially on the left side of the engine bay. They also said that grounds are a big issue as well. I checked all of the harnesses that I could find and everything is intact, nothing brittle or separated. Checked all connectors to make sure they are tight and sealed.

I noticed that there are several ground wires screwed into the fenders on both sides of the truck that are factory installed but the second battery (passengers side) only has a ground wire running to the engine block whereas the other battery has several ground wires coming from it. I installed a ground wire from the second battery to a bolt that has ground wires on it to see if that helps. Will check it out and post my findings.