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DTC codes / P0Cxx · Hybrid propulsion / P0C57

P0C57Drive Motor B Position Sensor Circuit A Circuit Low

P0C57 indicates that the powertrain control module has detected a low voltage condition on the 'A' signal circuit of the position sensor for drive motor B, which is the second electric motor in a hybrid or electric vehicle's propulsion system. The sensor reports the rotor position of drive motor B, and a low signal means the circuit is shorted to ground, open, or the sensor's output is below the expected range. This can affect motor control and may trigger reduced power or a shutdown of the hybrid system.

SystemPowertrain
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light or hybrid system warning light
  • Reduced engine power or limited vehicle speed, often entering limp mode
  • The vehicle may refuse to start or move, especially in electric-only mode
  • Rough running or shuddering during acceleration if the motor is still operating
  • Often no symptoms besides the warning light, particularly if the fault is intermittent

Common causes, most likely first

  1. Damaged or chafed wiring in the drive motor B position sensor circuit, especially near connectors or where the harness bends
  2. Corroded, loose, or water-intruded electrical connector at the position sensor or powertrain control module
  3. Internal failure of the drive motor B position sensor, such as a shorted or open sensing element
  4. Faulty powertrain control module, though this is less common and should be diagnosed last
  5. Poor ground connection for the sensor or motor assembly, causing a reference voltage drop
  6. Aftermarket or improper repairs that disturbed the sensor circuit, such as a poorly spliced wire

How to diagnose and fix it

  1. Perform a visual inspection of the drive motor B position sensor wiring and connectors for damage, corrosion, or loose pins
  2. Use a scan tool to check for related codes and freeze-frame data, and verify the sensor signal with a live data stream if available
  3. Measure resistance and voltage on the sensor circuit according to the manufacturer's service information, checking for shorts to ground or opens
  4. Disconnect the sensor and check for the correct reference voltage and ground at the connector, then inspect the sensor's internal resistance
  5. Repair or replace any damaged wiring, terminals, or connectors, and clear the codes to see if the fault returns
  6. If the circuit tests good, replace the drive motor B position sensor, following the proper relearn or calibration procedure
  7. As a last resort, diagnose the powertrain control module for internal faults after all other possibilities are eliminated

Before you replace the drive motor B sensor

  • A low signal code often results from a simple wiring problem, such as a pinched harness near the motor mount or a corroded connector, rather than a failed sensor.
  • Intermittent faults can be caused by vibration or temperature changes, so wiggle-testing the harness while monitoring live data is a crucial step that many technicians skip.
  • The position sensor shares its reference voltage or ground with other sensors in some designs, so a fault elsewhere can drag down the signal and set this code.
  • After replacing the sensor, some vehicles require a position offset relearn or calibration procedure; failing to do so can cause drivability issues or a repeat code.
  • This code does not always mean the motor itself is failing; the sensor circuit is a separate system, and misdiagnosing it as a motor fault leads to unnecessary and expensive repairs.

Can I keep driving with P0C57?

If the vehicle enters limp mode or the hybrid system warning is illuminated, avoid driving at high speeds or under heavy load, and proceed cautiously to a repair facility. Continued driving with a low position sensor signal can cause the motor to operate inefficiently or shut down unexpectedly, so it is safest to have the fault diagnosed promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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