Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P1635 (79): Battery Condition Monitor (BCM) Module Problem: General Description
The self-diagnostic function in the BCM (battery condition monitor) module checks the divided voltage of the ±12 V powersupply and the divided voltage of the 25 V DC-DC converter. If it is beyond a set value, a malfunction in the power-supply voltage to the sensor is detected and a DTC is stored.
| Execution | Continuous |
| Sequence | None |
| Duration | 2 seconds or more |
| DTC Type | One drive cycle, MIL ON, IMA system indicator ON |
| Condition | Minimum | Maximum |
|---|---|---|
| MCM power-supply voltage | 7.5 V | - |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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