P0C57

Code

Generic P — Powertrain

Drive Motor B Position Sensor Circuit A Low

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 25 RU: 23

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Page language: EN

Causes

Open circuit or broken wiring in position-sensor signal or reference circuit
Short to ground on the sensor signal wire
Failed position sensor (Hall sensor, encoder, or resolver)
Poor or corroded connector/terminal connection
Fault in inverter / motor controller (sensor interface or excitation)
Water, debris, or mechanical damage to sensor or motor

Symptoms

MIL / EV/HEV warning lamp illuminated
Reduced torque or limited power / limp-home mode
Drive motor may not engage or exhibits erratic behavior
Stored DTCs related to motor position or inverter faults
Possible inability to shift into drive or sudden torque cut

What to check

Read and record freeze-frame and all stored codes with a capable scan tool (EV/HEV-capable)
Visually inspect harness, connectors, and motor plug B for damage, corrosion, or water ingress
Check connector seating and terminal condition at motor, inverter, and control module
With vehicle powered appropriately (observe HV safety), check sensor reference voltage and ground at the connector
Monitor live sensor signal with scope or scan tool (oscilloscope preferred) while rotating motor or during run-down
Perform continuity and short-to-ground/short-to-battery checks on the signal and reference wires

Signal parameters

Hall/encoder-type sensors: DC-centered signal ~2.5 V with excursions ~0.5–4.5 V (varies by design)
Resolver-type sensors: differential sine/cosine AC signals, typical amplitude ~0.5–5 VRMS (depending on excitation)
Reference excitation typically 5 V (or resolver excitation frequency/voltage supplied by inverter) — verify with service data
Signal frequency should change proportionally with motor speed; amplitude should be within manufacturer limits
Resistance/contact values vary by sensor type — consult service manual before replacing based on ohms alone

Diagnostic algorithm

WARNING — follow all high-voltage and lockout/tagout procedures before working on EV/HEV high-voltage components.
Retrieve and record relevant DTCs and freeze-frame data. Note vehicle condition when code set (speed, temperature).
Clear codes and attempt to reproduce. If code returns, proceed with tests.
Perform a visual inspection of Drive Motor B harness and connectors for damage, chafing, corrosion, or water entry.
With low-voltage systems safe and ignition on (observe HV rules), back-probe the sensor connector and verify reference supply and ground presence using a DMM.
Monitor the sensor signal with an oscilloscope while rotating the motor shaft (or during a controlled motor run) and compare waveform to known-good pattern or the other circuit/phase. Look for flatline, low amplitude, or noisy signal.
If signal is low or absent, disconnect the sensor at the motor and check for open/short on the harness: continuity to controller, and short to ground or battery.
Wiggle test harness and connectors while monitoring signal to find intermittent faults.
If wiring checks good, inspect/measure the sensor element (resistance if specified) or replace sensor with known-good unit if available.
If replacing sensor does not clear the fault, suspect inverter/motor controller input stage. Verify controller outputs/excitation for resolver or reference for Hall sensors. Repair or replace controller as directed by manufacturer procedures.
After repair, clear codes and perform road/drive test including live-data verification to ensure the signal is stable across operating conditions.

Likely causes

Damaged wiring or connector to Drive Motor B position sensor
Failed position sensor element (Hall/encoder/resolver) on motor B
Short to ground in sensor signal circuit
Faulty inverter/motor controller input stage for that sensor channel

Fault status

⚠️ Status

Drive Motor B Position Sensor Circuit A Low — position-sensor signal below expected threshold (open/short/low amplitude). May cause torque limiting or limp mode.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.5 hours