B2556: BCM Enable Signal Short to Battery
Diagnostic trouble code B2556 indicates that the Body Control Module (BCM) has detected a short to battery voltage (B+) on the enable signal circuit for a specific submodule or component. This enable signal is typically a 12V wake-up line sent by the BCM to modules such as the audio amplifier, liftgate module, sunroof, or passive entry system. When the BCM senses voltage on this circuit when it should be low (0V) or floating, it sets the code to protect the communication network and the module itself.
1. Commonly Affected Makes
2. Most Common Causes
- Wiring harness short circuit between the enable signal circuit and a B+ power circuit
- Damaged BCM or receiving module connector with bent pins or corrosion bridging power and signal terminals
- Internal failure of the receiving module (e.g., amplifier, liftgate module) backfeeding battery voltage onto the enable line
- Internal failure of the BCM output driver keeping the line high permanently
- Improper aftermarket accessory installation (alarm, audio) bridging circuits
3. Symptoms You Will Notice
- Malfunction of the affected submodule (e.g., audio amplifier, liftgate, sunroof, passive entry)
- Possible battery drain or communication faults on the vehicle network
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data to identify the affected circuit
Visually inspect the BCM and receiving module connectors for damage, corrosion, or bent pins
Measure voltage on the enable signal circuit with the ignition off; it should be near 0V. If B+ is present, isolate the short by disconnecting modules one at a time
Check for aftermarket accessories tapped into the enable circuit and remove if found
If no external short is found, suspect internal BCM or receiving module failure and test by substitution
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but the affected component may not work properly and there is a risk of battery drain. Have it diagnosed soon.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on whether the issue is a simple wiring repair or requires module replacement.