First, you need to prepare some simple tools, including a wheel wrench, torque wrench, various sockets, extension bars, thread sealant, and a brand-new starter motor. Let's get started.

Step 1: Disconnect the negative terminal and ensure proper insulation. If you don't want to get electrocuted while removing the starter motor under the car, do not skip this step.

Step 2, disconnect the starter motor’s wiring harness. First, locate the starter motor, which is typically positioned between the engine and transmission. The power cables are connected here, specifically this cable and the inner cable. Use an extension bar with a socket to remove this cable first. Note that there are several washers on top; do not forget to remove them. Once removed, you can disconnect this cable and then remove the inner, thinner cable. This completes the removal of the starter motor’s power cables.

Step 3: Remove the starter motor's mounting screws. There is one screw here and another one inside. We can start by removing the inner screw. Use a socket wrench with an extension rod to loosen this screw. Once loosened, you will notice the starter motor has become loose. Therefore, be cautious when removing this screw, as the entire starter motor will begin to drop once removed. Ensure you support it with your hand during removal.

After removing it, we can see the reason why the starter motor cannot start the engine. It is quite obvious that this bearing has become severely loose, and the seal ring inside has fallen off by half, causing the bearing to become loose and move around inside. This causes the small gear inside to pop out and move around as well, preventing it from meshing properly with the engine's flywheel, naturally making it impossible to start the engine. Looking at the newly purchased starter motor, its bearing is very tight, with good sealing and no loosening at all.

Step 4: Install the new starter motor. Before installation, pre-insert the bolts into the starter motor, then apply thread locker to the threads of the bolts. This step is very important because the starter motor experiences significant vibration, so thread locker must be applied before installation.

Reinstall the new starter motor in its original position. Note that these two screws must be held steady by hand to prevent them from falling out during installation. Then thread the two screws through and tighten them with a wrench. However, this is not sufficient. A torque wrench must be used to adjust the torque to 45 Newton-meters according to the maintenance manual, and then tighten the two mounting screws. Next, reinstall the starter motor's power cables. First, connect the thick positive cable, then install the two washers and nuts. Use a wrench and extension bar to tighten the nut. Finally, connect the thinner inner cable. This completes the starter motor replacement.

Step 5: Reinstall the battery's negative terminal. Then start the car.