2020 Ford Explorer Battery Dead After Sitting? Here's the Fix

Key Takeaway

If your car's battery keeps dying, the most common and effective solution is to replace the rear body control module (RBCM). Based on owner reports, this single part is responsible for a significant number of parasitic drain issues. Before replacing it, you should test for a battery drain and check for related faults like a stuck turn signal relay or a faulty key fob, as these are cheaper fixes to try first.

Proven Fixes

Based on the analysis of 73 discussions, here are the solutions owners have used, ranked from the most frequently successful to more specific fixes.

1. Replace the Rear Body Control Module (RBCM): This is the heavyweight champion of fixes. The RBCM manages many of your car's electrical accessories (like interior lights, power locks, and sometimes turn signals). When it fails, it can prevent the car's systems from fully "going to sleep," causing a slow but steady battery drain overnight. Many owners reported this as the definitive fix after chasing other issues.

2. Check and Replace the Turn Signal/Hazard Relay: Several owners found that a faulty turn signal or hazard flasher relay was the culprit. This relay is often integrated into or controlled by the RBCM, which explains the connection. A stuck relay can keep a circuit active. This is a simpler and cheaper part to swap than the entire module.

3. Inspect and Re-seat Wiring Connectors: A surprising number of problems were solved by simply checking the wiring. Focus on the connectors to the RBCM (often located in the rear trunk or quarter panel) and the fuse box. Look for corrosion, bent pins, or connectors that aren't fully "clipped" in. A poor connection can cause all sorts of electrical gremlins.

4. Address Key Fob Issues: In some cases, a malfunctioning key fob constantly broadcasting a signal can prevent the vehicle from entering its full sleep mode. Try removing the battery from your key fob for a night or storing the fob farther away from the car to see if the drain stops.

5. Clear Diagnostic Trouble Codes (DTCs): Specific OBD codes like B1533 (often related to door ajar switches or lighting circuits) and B1497 (related to hazard switch input) were mentioned. Sometimes, clearing these codes with a scan tool can resolve the issue if it's a software glitch, but they often point back to the physical problems above.

Recommendation: Start with the simple, no-cost tests. Try the key fob trick and inspect all visible connectors. If that doesn't work, locate and swap the turn signal relay (often under the dash). If the drain persists, the RBCM is the most likely candidate.

Testing Procedures

You need to confirm you have a parasitic drain before throwing parts at the problem. Here’s how to do it safely.

What You'll Need: A digital multimeter (DMM).

Safety First: Always wear safety glasses. Ensure all doors, the trunk, and the hood are fully closed and latched. Remove the key from the ignition and lock the doors with the mechanical key if possible to simulate the car's normal "sleep" state. Wait at least 20-30 minutes for all modules to power down.

The Test:

1. Set your multimeter to measure DC Amps (usually the 10A setting).
2. Disconnect the NEGATIVE battery terminal.
3. Connect the multimeter in series between the negative battery post and the disconnected negative cable. (Red probe to cable, black probe to battery post).
4. Read the meter. A normal parasitic drain is typically between 0.020A and 0.050A (20-50 milliamps).
5. If your reading is significantly higher (e.g., 0.2A or 200mA+), you have a confirmed drain.

Pinpointing the Drain: With the meter still connected, start pulling fuses one by one from the interior and under-hood fuse boxes. Watch the multimeter. When you pull the fuse that makes the amp drop dramatically, you’ve found the circuit causing the problem. Consult your owner's manual to see what that fuse powers—it will lead you directly to the faulty component (like the "Turn Signal" or "Body Control" circuit).

Why This Happens

These battery drain issues are almost never the fault of the battery itself. They are caused by an electrical component that fails to shut off. The Rear Body Control Module is a common point of failure because it's a complex computer that controls multiple always-on systems. Over time, internal circuits can short or transistors can fail, keeping it partially awake.

The related issues with turn signals and key fobs happen because they are directly tied into this network. A stuck relay is a mechanical failure inside a component, and a "chatty" key fob continuously wakes up the car's receiver, thinking you're about to unlock it.

Symptoms Reported by Owners

Owners described a very consistent pattern:

• Dead Battery Overnight: The most common report—the car starts fine in the evening but is completely dead the next morning.
• Intermittent Starting Issues: The car might start sometimes but fail at other times, especially after sitting for a few hours.
• Electrical Gremlins: Owners noted weird behavior like turn signals not working, interior lights staying on, or the keyless entry acting up before the battery died.
• Diagnostic Trouble Codes (DTCs): Codes like B1533 and B1497 were frequently present when scanned, pointing to body control system faults.

What to Expect to Pay

Costs can vary widely based on the fix and whether you DIY.

• DIY (Do-It-Yourself):

  • Turn Signal Relay: $15 - $50 for the part.
  • Key Fob Battery: $3 - $10.
  • Rear Body Control Module (RBCM): $150 - $400 for a new or used module. Important: A new module often requires programming at a dealership or specialized shop, which adds to the cost.
  • Multimeter for Testing: $25 - $60 (a one-time tool investment).

• Professional Repair:

  • Diagnostic Fee: $100 - $150 for a shop to perform a parasitic drain test.
  • RBCM Replacement with Programming: $450 - $800+ is a common total range. This includes 1-2 hours of labor for diagnosis and installation, plus the part and programming time.

Starting with the DIY diagnostic test can save you hundreds of dollars, even if you ultimately need a pro to program a new module.

Common Questions

Q: Can a bad battery cause these symptoms? A: Yes, a failing battery can mimic some symptoms, but the pattern is different. A bad battery usually struggles in all conditions (cold mornings, after short drives). A parasitic drain causes a healthy battery to go dead specifically after the car sits. Testing the battery at a parts store is a good first step to rule it out.

Q: Do I have to go to the dealer to fix this? A: Not necessarily. A competent independent mechanic with the right scan tools can diagnose and often perform the repair. However, programming a new RBCM almost always requires a dealer-level or high-end aftermarket scan tool, so you may end up at the dealer for that final step.

Q: Is it safe to drive with this problem? A: You can drive it as long as the battery is charged, but it's unreliable. You risk being stranded. It's best to diagnose and fix it promptly, as constantly jump-starting and deeply discharging the battery will ruin a good battery quickly.

Q: I cleared the B1533/B1497 codes and they came back. What does that mean? A: It means the problem is a persistent hard fault, not a temporary glitch. The code is a symptom, not the cause. It's telling you there is an ongoing electrical problem in the circuit it monitors, which aligns perfectly with the faulty RBCM or relay theory.

Source Summary: This analysis is based on 73 owner discussions from Reddit and automotive forums.