* Faulty ABS Module (Control Unit): This is the most common cause. The module itself is malfunctioning and not properly shutting down. Internal shorts or failures within the module can lead to this constant draw.
* Low Battery Voltage: A weak battery might not provide enough voltage to fully power down the ABS module. This doesn't mean the battery is completely dead, just low enough that the module doesn't receive a clean shutdown signal.
* Wiring Problems: A short circuit in the wiring harness connected to the ABS module could prevent the power from being interrupted when the ignition is off. This could be a damaged wire, a corroded connection, or a short to ground.
* Stuck Relay: While less common, a relay related to the ABS system might be stuck closed, constantly supplying power.
* Body Control Module (BCM) Issue: In some cases, a problem with the BCM can prevent it from correctly signaling the ABS module to shut down.
Troubleshooting Steps (in order of safety and ease):
1. Check the Battery Voltage: A low voltage reading (below 12.5 volts) indicates a weak battery or charging system problem. This should be addressed regardless of the ABS issue.
2. Disconnect the ABS Module Battery Cable: This is a crucial safety step. Locate the ABS module (usually under the hood or near the master cylinder). Carefully disconnect the negative battery cable connected directly to the ABS module itself. *Only disconnect the cable to the module, not the main battery terminals*. If the pump stops running after disconnecting the cable to the ABS module, then the problem almost certainly lies *within* the ABS module or its wiring.
3. Visual Inspection of Wiring: Once the ABS module cable is disconnected, carefully examine the wiring harness for any damage, corrosion, or broken connections near the ABS module.
4. Professional Diagnosis: If the problem persists after checking the battery and wiring, you'll need professional help. A mechanic with a scan tool can diagnose the ABS module for fault codes, which can pinpoint the exact problem. They can also test the relays and other components associated with the ABS system.
Important Note: Do not attempt to repair the ABS module yourself unless you have significant electronic repair experience. The ABS module is a complex electronic device, and improper repair could cause further damage or even safety hazards. It's usually best to replace a faulty module. The constant drain on your battery can lead to it being completely drained.
