When It Failed
When your Toyota hybrid displays a Check Engine light along with a "Hybrid System Check" message, don’t immediately assume the hybrid battery has failed. These warnings can be triggered by a variety of issues, ranging from from cooling system issues, sensor faults, or other hybrid system problems.
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Scan for Trouble Codes (DTCs)
Use an OBD2 scanner—preferably a Toyota Techstream or a high-quality hybrid-compatible scanner—to retrieve the diagnostic trouble codes. Some codes have sub-codes that provide more specific details about the issue, so be thorough in your scan. These codes will help pinpoint the exact problem rather than relying on guesswork.
Here are some common Hybrid DTCs
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Early Warning Signs of Hybrid Battery Failure:
Before complete failure, a deteriorating hybrid battery often shows warning signs, including:
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Drop in fuel efficiency – The internal combustion engine runs more frequently to compensate for reduced battery performance.
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State of Charge (SOC) fluctuations – The battery indicator bars on the dashboard jump up and down erratically, suggesting poor capacity.
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