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Persistent Battery Drain on 2017 Ram 2500 - What's Drawing Power?

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Melissa G. · rep 0 · May 22, 3:34 AM · 1 replies · solved · Question

Vehicle: 2017 Ram 2500 Big Horn

My 2017 Ram 2500 Big Horn with the 6.4L Hemi keeps having its battery die after sitting for just a couple of days. It's incredibly frustrating, especially when I need to get to work.

I've already replaced the battery, and the alternator tests good, so I'm pretty sure it's a parasitic draw somewhere. I've tried pulling fuses one by one, but haven't found the culprit yet. It seems like a slow drain, but enough to kill the battery.

Has anyone dealt with a similar issue on their Ram 2500? What are the common modules or components that tend to cause a parasitic draw? I'm looking for some direction before I take it to the shop.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:34 AM

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ClearTheCode admin answer:

A parasitic battery drain on a 2017 Ram 2500 can be a challenging issue to diagnose due to the complexity of modern vehicle electrical systems. It means something is drawing power even when the vehicle is off and all accessories are supposed to be shut down.

Common Causes of Parasitic Draw in Rams:

  • Radio/Uconnect Module: These modules can sometimes fail to enter 'sleep' mode.
  • Body Control Module (BCM): A faulty BCM can keep various systems active.
  • Door Ajar Switches/Interior Lights: A switch that thinks a door is open can keep interior lights or modules awake.
  • Aftermarket Accessories: Improperly installed aftermarket stereos, alarms, or remote starters are frequent culprits.
  • Alternator Diode Failure: Even if the alternator charges, a failing diode can allow current to leak back to ground.
  • Glove Box/Underhood Lights: Sometimes these lights stay on due to a faulty switch.

Troubleshooting Steps (Parasitic Draw Test):

  1. Charge Battery Fully: Ensure your battery is fully charged before starting.
  2. Connect Ammeter: Disconnect the negative battery cable. Connect a multimeter in series between the negative battery post and the negative battery cable, set to measure amps (A or mA). Close all doors, hood, and trunk, and let the vehicle 'sleep' for 15-30 minutes (modules can stay active for a while after shutdown).
  3. Establish Baseline: A normal parasitic draw should be around 20-50 mA (0.02-0.05 Amps). If it's significantly higher, you have a draw.
  4. Pull Fuses: While monitoring the ammeter, systematically pull one fuse at a time from the fuse box (underhood and inside the cabin). When the amperage drops significantly, you've found the circuit responsible. This can help narrow down the faulty component.
  5. Check OBD Codes: A P0562 (System Voltage Low) or similar code might indicate a general power issue, but specific parasitic draw codes are rare.

When to See a Shop:

  • If you're uncomfortable performing the parasitic draw test yourself.
  • If you've identified a circuit but can't pinpoint the specific component.
  • If the draw is intermittent or difficult to reproduce.
  • A professional can use advanced diagnostic tools to isolate the exact module or wire causing the issue, especially if it's a BCM or Uconnect-related problem.
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