P0C50: Drive Motor A Position Sensor Circuit A
What to do
Losing one channel of a resolver loses the angle completely — the two channels are halves of one measurement, not a spare. Expect electric drive to be cut rather than reduced. Before a sensor is replaced, ask whether the wiring and its shielding were checked: these are low-level analogue signals and a resistive joint or a disturbed screen produces exactly this. Nothing here is a home job.
What this code means
Channel A of the position sensor on drive motor a has a circuit fault.
Two things need separating before this makes sense, and the corpus carries both.
First, this is not the same code as P0A3F. That one names the position sensor as a whole; these name its individual channels. The same shape as the current sensors at P0BE5 — a whole-thing code beside per-channel codes — and the same trap if they are read as duplicates.
Second, and this is the good part: channel A and channel B are not two sensors, and they are not redundant. A resolver reports rotor angle as two signals — one proportional to the sine of the angle, one to the cosine. Either alone is ambiguous: a sine value of one half is consistent with thirty degrees and with a hundred and fifty. Only the two together give a unique angle. So losing one channel does not degrade the measurement, it destroys it, and the inverter has no idea where the rotor is.
And the pair carries a self-check that costs nothing, which is the third time this block has used the trick. Sine squared plus cosine squared equals one, at every angle, always. So the module can verify its own position measurement against a mathematical identity — exactly as it sums the three phase currents to zero at P0BFD, and checks the planetary speed equation at P0C2F. When the sum of squares drifts away from one, something is wrong with a channel even though both signals still look like plausible waveforms.
That is what most Range/Performance faults in this family are: not a dead channel, but a channel whose amplitude has drifted, usually because a connection has gone resistive or shielding has been disturbed.
Likely causes
Start here
- Faulty motor position sensor · specialist
- Corroded or loose connector · easy
Less common
- Chafed harness between transaxle and inverter · specialist
- Failed sensor reference voltage supply · moderate
- Motor position sensor incorrectly fitted or misaligned · specialist
Symptoms
Components involved
Information, not instruction
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Community experience
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