P0A57

Code

Generic P — Powertrain

Drive Motor B Current Sensor Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 26 RU: 12

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Page language: EN

Causes

Open or shorted wiring in the motor B current sensor circuit (short to ground)
Corroded, loose or damaged connector at the current sensor, inverter, or control module
Faulty motor B current sensor (Hall-effect or shunt-based sensor)
Faulty inverter/drive module or internal sensor electronics
Low or missing reference voltage or ground to the sensor
Intermittent connection caused by vibration or heat

Symptoms

Hybrid/EV system warning light or MIL illuminated
Reduced torque, limited power or limp mode
Loss of regenerative braking or abnormal charging behavior
Stored fault code(s) for motor current sensor circuit
Possible unusual noises from inverter/motor under load (rare)

What to check

Retrieve all diagnostic trouble codes and freeze frame data with an OBD-II / hybrid-capable scanner
Verify whether the code is current or historical; note any related codes (inverter, HV system, CAN bus)
Visually inspect connectors and wiring for damage, corrosion, pin push-out, or water ingress
Check continuity and insulation to ground for the sensor signal and reference wires with power removed
Measure sensor supply/reference voltage and ground at the connector with key ON (following safety procedures)
Backprobe the sensor signal with the system powered (observe HV safety) and observe voltage vs expected idle value

Signal parameters

Typical Hall-effect/current-sensor output: approx. 2.5 V nominal (no current), varying within 0–5 V range depending on current direction and magnitude (consult OEM spec)
Reference/supply voltage typically 5 V (or vehicle-specific) and a stable ground reference
Low-signal DTC triggers when sensor output falls below expected minimum threshold (often significantly below midscale reference)
CAN/inverter current message values may show abnormally low or implausible current readings

Diagnostic algorithm

Read and record DTCs and freeze frame data with a compatible scanner; note vehicle state when code set.
Visually inspect all accessible wiring and connectors between motor B, inverter/drive module, and control unit. Repair any damage.
With appropriate HV/12V safety procedures, backprobe the sensor connector and measure reference supply and ground continuity. Compare to OEM specifications.
Measure the sensor signal voltage with the system energized (follow safe procedures). Confirm if voltage is low relative to expected nominal (e.g., ~2.5 V no-load).
Check for short to ground on the signal wire (power off): measure resistance from signal to chassis ground and to supply. Repair short or open as needed.
Wiggle test harness/connectors while monitoring the signal for intermittent faults. Tighten or replace connectors as required.
If wiring and connectors test good, consult service manual for sensor-specific bench tests; if allowed, replace or swap the current sensor or inverter assembly to confirm.
If swap not possible, inspect inverter/drive for internal damage and consider replacement or professional inverter repair.
After repair, clear codes, perform system relearn if required, and test drive to confirm the fault does not return.
If code persists, escalate to specialized HV diagnostic/repair facility.

Likely causes

Wiring shorted to ground between sensor and inverter/ECU
Damaged connector pins or corrosion at sensor/inverter connector
Failed current sensor inside the inverter/drive assembly
Faulty inverter/drive electronics reporting incorrect sensor reading

Fault status

⚠️ Status

Drive Motor B Current Sensor Circuit Low — control module detects abnormally low sensor voltage/signal on motor B current-sensing circuit. Possible wiring short/open, faulty sensor, or inverter/controller fault. Vehicle may limit power and set hybrid/inverter warnings.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 2.0-6.0 hours