: Before replacing hybrid components, ensure the 12V auxiliary battery is fully charged and healthy .

Once you have diagnosed the root cause, here is the repair plan:

Unlike a standard "Crankshaft Position Sensor" code or a "Fuel Pump" code, P1D687A is a conclusion code . The vehicle’s Engine Control Unit (ECU)—known in Mercedes terminology as the ME-SFI (Motor Electronics - Sequential Fuel Injection) control unit—has attempted to crank the engine and has determined through various physical parameters that the engine itself is mechanically unable to turn.

Connect a professional-grade scanner

A: Temporarily, yes. For 10-30 minutes. But the code will return once the ECU runs its next BMS self-test (usually after 2-3 engine starts).

Measure voltage at BMS master connector – must be >11.5V during cranking.

The PCV valve’s job is to recycle "blow-by" gases from the crankcase back into the engine to be burned. If it fails, pressure can build up, leading to oil leaks, rough idling, or reduced engine performance. Common Symptoms