Tesla Model Y 2021 Hard Starting Diagnosis
The 2021 Tesla Model Y is experiencing increasingly prolonged cranking or failure to start. This is likely due to a failing 12V auxiliary battery, a degraded high-voltage battery, or a software/firmware issue affecting the startup sequence.
Diagnosis Details
Possible Causes
12V auxiliary battery failure: The 12V battery powers the contactors and BMS; when weak, startup delays occur.
High-voltage battery degradation or imbalance: Reduced capacity or cell imbalance can cause the BMS to take longer to verify readiness.
Firmware/software glitch: A bug in the startup sequence or BMS logic can cause intermittent or worsening delays.
Related OBD-II Codes
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What You Should Do
First, check the 12V battery voltage (should be >12.4V at rest).
If low, replace the 12V battery.
Next, perform a full system diagnostic via Tesla service mode or scan tool to check high-voltage battery health and BMS logs.
Update firmware to latest version.
If issue persists, contact Tesla service for high-voltage battery assessment.
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Disclaimer: This AI-generated diagnosis is for informational reference only. Always consult a qualified mechanic for an in-person inspection. AutOwner is not responsible for decisions made based on this information.
