* Bad Starter Motor: This is the most common reason. The solenoid inside the starter might be failing (it engages the gear to the flywheel), the gear itself might be stripped or jammed, the brushes might be worn out, or the motor windings could be damaged. A simple tap on the starter with a wrench (while someone tries to crank the engine) can sometimes temporarily solve this if it's a sticking solenoid, but it's only a temporary fix.
* Bad Starter Solenoid: The solenoid is the electrical switch that activates the starter motor. It might be failing to engage the starter motor even if it's getting power. This can often be tested with a multimeter.
* Bad Battery Cables/Connections: While you say you have power *to* the starter, weak or corroded battery cables (positive and negative) can still prevent sufficient current from reaching the starter motor to crank it over. Check for corrosion and ensure tight connections at both the battery and starter terminals.
* Neutral Safety Switch: This switch prevents the engine from starting unless the transmission is in Park or Neutral. A faulty neutral safety switch won't allow the starter circuit to close even if the key is turned. This is a relatively common failure point.
* Ignition Switch: Although less likely if you have power *to* the starter, a failing ignition switch could be preventing the proper signal from reaching the starter solenoid.
* Low Battery Voltage (despite having "power"): While you may have some voltage, insufficient cranking amps from a weak battery can prevent the starter from turning the engine over. A battery load test is needed to determine this.
* Flywheel Issues (Less likely, but possible): A damaged or seized flywheel can prevent the starter from turning it, even if the starter itself is functioning. This would usually manifest as a loud grinding noise, but it's possible a seized flywheel only prevents turning.
Troubleshooting Steps:
1. Check Battery Cables and Connections: This is the easiest and first step. Clean and tighten all connections.
2. Test the Battery: Make sure the battery is properly charged and has sufficient cranking amps (load test).
3. Listen Carefully While Cranking: Are there any unusual sounds (grinding, clicking, whirring)? This can help pinpoint the problem.
4. Tap the Starter (carefully!): A gentle tap with a wrench *might* temporarily fix a sticking solenoid, but this is not a long-term solution.
5. Test the Starter Solenoid (requires a multimeter): This involves testing voltage and continuity at the solenoid terminals.
6. Check the Neutral Safety Switch: Ensure the transmission is in Park or Neutral and check the switch itself for proper operation. A simple test can often be done with a multimeter.
If you're not comfortable performing these tests yourself, it's best to take your Tahoe to a qualified mechanic for diagnosis and repair. Attempting to work on a starter motor without the proper knowledge and tools can be dangerous.
