Cummins P2509 Engine Code – Disagnosis & Troubleshooting

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When you scan your Dodge/Ram Cummins engine and receive a P2509 diagnostic code, it will read ‘ECM/PCM Power Input Signal Intermittent Code’.

P2509 appears on Cummins engines when there is an electronic signal being sent to the ECM/PCM that is faulty or intermittent. Electronic signals are measured within parameters, and when the signal falls outside of the parameter range, the Power Input Signal Intermittent Code P2509 is thrown.

A Cummins P2509 engine code is a battery related issue. Either your battery is weak and running low voltages, something is draining your batter faster than it can charge, or there is a poor electrical connection. While all signs point to the battery, this trouble code can actually be caused by a number of issues, and replacing the battery isn’t always the answer.

Causes of a P2509 Fault Code

Most Cummins diesel engines have a dual-battery setup. One battery is located on the driver side, and one on the passenger side within the engine bay. For most Cummins owners, P2509 is an issue with the driver-side battery. The majority of owners report that changing the battery solves the problem.

However, replacing the battery isn’t always the answer. This fault code can also be caused by:

  • Driver side battery failure
  • Bad battery connection (check connector cables)
  • Bad alternator (over or undercharging batteries)
  • Corroded battery cables
  • Leaking batteries

If you are getting this fault code and have checked your battery connection, cables, and voltage, your issue could be your alternator. A weak alternator can cause your Cummins to not be able to start or continue running. Test your alternator and replace this if you don’t have any battery issues.

Cummins P2509 Fault Code Symptoms

The obvious symptom is the code itself, however, some additional symptoms may appear:

  • Check engine light with P2509 code
  • Hard start, no start (will usually still crank)
  • Rough idling after engine start
  • Battery voltage indicator is below 11 volts
  • Engine shutoff while driving (if battery is being drained faster than charged)
  • P2502 and P2503 codes

P2502 and P2503 Codes

These codes are known to appear alongside the P2509 code and will read ‘Charging System Voltage Low’. When you receive these codes all together, you might need to have your PCM reprogrammed.

Dodge/Ram released a Technical Service Bulletin (TSB) with number 18-001-07. Pre-2006 Cummins trucks had a common issue relating to a “check gauges” light combined with these three engine codes. A PCM programming malfunction is the result of this and can be fixed by taking your truck to a Dodge dealer and having them reprogram the PCM.

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  1. Thank you for posting this, I got this code this morning and when the check engine light came on my heart sank. But this isn’t that Huge of a problem. Just had a question as a follow up to this article, could really cold nights and the vehicle parked on the street contribute to this? I replaced my batteries last year with Optima Red Tops when I moved to Utah and this year we’ve had a much colder winter than last year. (I moved here from California, so cold is relative). I was just wondering is this could be a contributing factor. Thanks in advance for any help you might be able to offer.

  2. I have this code repeating periodically, usually during the cold season, mechanic said a battery warmer might help. It doesn’t affect anything, it starts, runs smoothly, and is seen regularly by the mechanic. I have asked a couple other mechanics about it and they all say the same thing, at least for my truck, its not a problem. However, it won’t pass CA smog with the light on, so I got a code reader and I clear the code before I take the truck to the smog station during the summer. On my truck, 2003 Dodge Ram 2500, the code usually comes up during the cold weather.

  3. My 2007 has a 2509 code along with a u1403 code.
    Engine starts but then stalls after a few attempts it will stay running

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