A 2022 Rivian R1T arrived at our workshop with a problem that cannot be solved by basic guessing. The vehicle came in because the 12V battery kept discharging. The high-voltage system was not connecting at all, so it was clear that the cause was not just the 12V battery itself.
With electric vehicles, the diagnostic process has to be systematic. If the 400V circuit does not activate, the 12V battery has no source of charging and the vehicle can repeatedly lose power. That is why we started with full system diagnostics and searched deeper in the drivetrain.
The first symptom was simple: the 12V battery kept discharging. Replacing the battery alone would not solve the issue if nothing was charging it. That is why we checked why the high-voltage system was not connecting.
We focused on:
Diagnostics showed that the 400V system was not activating. That meant the cause was deeper than a regular weak battery.
Without an active 400V circuit, the 12V battery has no charging source. Therefore, the cause had to be found in the high-voltage components.
Further inspection included:
Suspicion pointed to the left electric motor. To verify the fault, the motor had to be removed and checked more precisely outside the vehicle.
We removed and measured the left electric motor. The check was performed between phases and against the housing, because this is where internal faults can appear and cause the system to refuse high-voltage activation.
We carried out:
The result confirmed an internal fault in the electric motor. The verdict was clear: the motor could not be repaired through a normal service procedure and needed replacement.
If the high-voltage system does not activate, the 12V battery has no charging source. The cause can be in electronics, control units, or high-voltage components.
It means the high-voltage circuit is not connected, and the vehicle cannot properly power systems that depend on it. In an EV, this is a serious fault.
Some faults can only be confirmed after removal and measurement between phases or against the housing. This helps detect an internal short circuit or other motor damage.
The 2022 Rivian R1T arrived with a repeatedly discharged 12V battery and an inactive high-voltage system. Diagnostics showed that the problem was not the regular battery, but the 400V circuit. Suspicion pointed to the left electric motor, which we removed and measured between phases and against the housing. The test confirmed an internal motor fault. The result is a clear verdict: the motor needs replacement.
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