Diagnosis
The alternating red and green flashing light sequence on the Makita XWT15Z is the tool's integrated protection circuit signaling a critical fault. Specifically, this is a "Protection Mode" trigger. It occurs when the brushless controller detects an anomaly that could cause permanent damage to the motor windings or the electronic control unit (ECU). The most common root cause is thermal overload, where the internal thermistor detects that the motor or the battery cells have exceeded safe operating temperatures. However, this code also triggers during a "stalled rotor" event. If the tool hits a hard stop or the fastener is completely seized, the current spike causes the controller to cut power instantly to prevent the MOSFETs from blowing. You can confirm this by checking if the tool was under heavy load immediately before the failure. If the tool flashes this code upon a cold start without any load, the issue is likely a communication failure between the LXT battery's intelligence chip and the tool's internal logic board, or a short circuit in the trigger switch assembly.
How to Fix It
To reset the protection circuit and restore functionality to your XWT15Z, follow these precise steps:
- Immediately release the trigger and remove the 18V LXT battery from the tool housing. This breaks the circuit and allows the ECU to clear the temporary fault state.
- Allow the tool and the battery to cool for at least 15 to 20 minutes. Do not attempt to "test" it every 30 seconds, as the thermal sensor requires a specific temperature drop before it will release the lock.
- Inspect the 1/2" square drive anvil. Ensure there is no debris jammed in the anvil or a socket that has become fused to the drive. If the tool was stalled on a bolt, use a manual breaker bar to loosen the fastener first.
- Inspect the battery terminals. Ensure no metal shavings or conductive dust have entered the battery slot.
- Insert a fully charged battery (preferably a 5.0Ah or higher for maximum current stability). Push the battery in until you hear a distinct click, ensuring the gold-plated pins are fully seated.
- Squeeze the trigger halfway to initiate the motor. If it spins, gradually increase pressure to full power.
If That Didn't Work
- Clean the Communication Terminals: Use a cotton swab dipped in 90% isopropyl alcohol to clean the gold-plated contact pins on both the battery and the tool. A thin layer of oxidation or grease can disrupt the data signal between the battery's BMS (Battery Management System) and the tool, triggering a false overload code.
- Swap the Battery Pack: Test the tool with a different 18V LXT battery. If a different battery works, the original pack has a failing cell or a tripped internal breaker that is sending an "over-current" signal to the tool.
- Check the Trigger Switch: If the red/green flash occurs the moment you touch the trigger (without load), the switch assembly may be intermittently shorting. Use compressed air to blow out the trigger housing to remove any metallic dust that may have entered the casing.
- Inspect for Internal Wire Chafing: If you are comfortable opening the casing, check the wiring harness leading from the motor to the control board. Vibration can sometimes chafe the insulation, causing a momentary short that triggers the protection circuit.
Heads Up
- Avoid "hammering" the trigger repeatedly when the tool stalls; this generates heat rapidly in the brushless controller and will trigger the red/green code more frequently.
- Always use high-quality impact-rated sockets. Using standard chrome sockets can cause the tool to slip or kick back, which creates the erratic current spikes that trip the ECU.
- Store your batteries in a temperature-controlled environment. Extreme cold or heat can cause the battery's internal resistance to spike, leading the tool to believe there is a motor overload.
- If the red/green flashing persists even with a brand new battery and no load, the internal control board (ECU) has likely suffered a hardware failure and requires replacement.