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 P1648 (75): Motor Control Module (MCM) Communication Signal Circuit Problem: General Description
Data is transmitted and received between the MCM (motor control module) and the BCM (battery condition monitor) module. Various commands are included in the data stream, and commands are not completed, which is normal, when there is an open in the line or a faulty circuit for the interface. The BCM module measures a time interval during which the command update has not been executed based on updates by the internal timer. If the time interval is beyond a set time, the BCM uses a full-safe value, then provides timing for the MCM to signal a abnormality of the data received from the MCM. The data update is resumed when the normal data is received, and the fail-safe maintains the latest value. If no data updates are executed over a set time, a malfunction is detected and a DTC is stored.
| Execution | Continuous |
| Sequence | None |
| Duration | 4 seconds or more |
| DTC Type | One drive cycle, MIL ON, IMA system indicator ON |
| Condition | Minimum | Maximum |
|---|---|---|
| BCM 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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