Technical Description of OBD-II Trouble Code
Intermittent Signal for ECM/PCM Power Input
What does that signify?
This is a generic code related to the powertrain, which applies to all vehicles that support the OBD-II protocol. However, the specific troubleshooting steps may vary depending on the vehicle.
The generic trouble code P2509 indicates an intermittent electrical signal to the Electronic Control Module (ECM), also known as the PCM or Powertrain Control Module.
The signal is not consistently within the required parameters when the ignition key is turned off. The voltage from the batteries may be low, dropping due to a power drain, or there may be a faulty connection.
A small amount of parasitic draw, typically 30 milliamps or less, is normal after the computer systems have gone to sleep or timed out. This draw is caused by the ECM memory and radio memory, but it is insignificant and does not affect battery performance.
This code is most commonly found in Dodge & Ram diesel trucks. Technical service bulletins for the Dodge/Ram Cummins diesel engine also suggest that an overcharge or undercharge condition can contribute to the occurrence of this code and its associated symptoms.
Symptoms
The symptoms of a P2509 engine code may include:
Potential Causes
The potential causes for this DTC may include:
Diagnostic and Repair Procedures
Special note for Dodge/Ram Cummins diesel owners: There is a technical service bulletin (TSB), number 18-001-07, that may be applicable to your 2006-older truck and can resolve the issue. The fix mentioned in the bulletin is to reprogram the PCM. You may also encounter the “check gauges” warning lamp and have a P2502 and/or P2503 DTC along with the P2509 code.
Test the batteries to check their charge. Use a voltmeter and place the probes on both terminals. A fully charged battery should display a voltage of about 12.75 volts. If the batteries have a voltage lower than 12 volts, charge them before proceeding. It is pointless to check a discharged battery.
Checking battery voltage using a digital voltmeter:
In the case of dual batteries, if one battery has a significantly lower voltage than the other, it is likely to be faulty. The low battery is not charging at the same rate and may have one or more bad cells. If the caps are removable, remove them and check the water level in all cells. If one or more cells have a lower water level than the adjacent cells, it is likely that those cells are bad.
Check all the cells using a hydrometer. Good cells should have a specific gravity of 12.60. If all cells have low specific gravity, it indicates a discharged battery. If one or more cells have a specific gravity lower than 12.60, it means that those cells have shorted and the battery is faulty.
If a hydrometer is not available, use a voltmeter across the terminals of the fully charged batteries. Attempt to start the engine and note the voltage drop on both batteries. If the voltage drops below 10.5 volts, the battery is faulty. In 32-degree temperatures, the voltage should be no less than 9.5 volts.
If the battery (or batteries) do not fully charge, they are faulty. If they are faulty under any of the above circumstances, replace them. However, that is not the end of the issue. The next question to answer is why they are discharged or faulty.
