* Battery Cables and Connections: Corrosion or loose connections on the battery terminals, the starter cable, or the ground cable can prevent sufficient current from reaching the starter motor. Clean and tighten all connections thoroughly. Check for any breaks or significant wear in the cables themselves.
* Battery: Even if the battery tests "good" with a simple voltage test, it might not have enough *cranking amps* (CCA) to turn the engine over, especially in cold weather or if the battery is old. A load test at an auto parts store is more definitive.
* Neutral Safety Switch (NSS) or Park/Neutral Position Switch: This switch prevents the starter from engaging unless the transmission is in park or neutral. A faulty NSS will prevent the starter circuit from completing.
* Ignition Switch: The ignition switch might be failing, preventing power from reaching the starter solenoid.
* Starter Solenoid: While you've tested the starter motor itself, the solenoid (the clicking part on the starter) could be faulty. It's possible the motor is fine, but the solenoid isn't engaging. A common symptom of a bad solenoid is a clicking sound when you turn the key.
* Ignition Coil: While this is less likely to prevent cranking entirely, a bad ignition coil could cause weak sparking, which might be mistaken for a cranking issue.
* Wiring Issues: A broken or corroded wire somewhere in the starting circuit can interrupt the power flow. This requires a more thorough visual inspection of all wiring related to the starter.
* Security System: If your Tahoe has an aftermarket security system or alarm, it might be preventing the starter from engaging.
Troubleshooting Steps:
1. Check battery cables and connections: This is the easiest and most common fix.
2. Battery load test: Have the battery load tested at an auto parts store to determine its CCA.
3. Listen for clicks: If you hear clicking when you turn the key, it often points to a bad battery, bad cables, or a faulty solenoid.
4. Check the neutral safety switch: Make sure the transmission is in park or neutral and that the switch itself isn't faulty. This often involves some electrical testing with a multimeter.
5. Test the ignition switch: This usually requires more advanced electrical testing.
If you're not comfortable working with car electrical systems, it's best to take your Tahoe to a qualified mechanic for diagnosis and repair. Improperly handling car electrical systems can be dangerous.
