Code
P0EA9
Generic
P — Powertrain
A/C Compressor Motor Voltage Sensor B Circuit Performance
Views:
UK: 19
EN: 22
RU: 24
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in sensor B circuit
- Poor connector contact, corrosion, or bent pins at sensor or control module
- Faulty A/C compressor motor voltage sensor (Bank B / Sensor B)
- Faulty inverter / compressor drive module that supplies or measures the sensor
- Low battery or unstable vehicle supply voltage
- Intermittent wiring damage due to chafing or heat
Symptoms
- Reduced or no A/C cooling (compressor disabled or not running)
- HVAC system warning or message (may show reduced function)
- Related DTCs stored for A/C compressor or inverter
- Possible audible abnormal noises from compressor/inverter when attempting to run
- Intermittent operation of A/C or loss of commanded compressor engagement
What to check
- Read and record freeze-frame and all stored codes; note any additional A/C/inverter codes
- Visually inspect compressor/inverter connector and wiring for damage, corrosion, pin push-out or melting
- Verify battery state of charge and vehicle supply voltage under load
- Check related fuses, relays and power feeds to the inverter/compressor
- Backprobe the sensor B connector and check for expected reference, signal and ground at rest and with compressor commanded ON
- Compare sensor B readings to sensor A (if present) using a scan tool
Signal parameters
- Typical signal type: analog DC level or PWM related to motor voltage — exact waveform depends on manufacturer
- Common voltage ranges to expect: 0–12 V on motor voltage sense lines; some systems use a lower 0–5 V reference-scaled signal
- Some inverter-driven compressors use PWM or high-frequency sensing; frequency content can be up to several kHz
- Compare live sensor B values to sensor A or to manufacturer specification; look for stuck, fluctuating, or out-of-range voltages
- Signal impedance (if specified by manufacturer) and continuity should be within expected limits
Diagnostic algorithm
- Retrieve codes and freeze frame data; note vehicle conditions when fault set (ignition, vehicle speed, A/C on).
- Visually inspect the compressor/inverter, harness and connectors for damage, heat discoloration or corrosion. Repair obvious damage.
- Verify battery voltage and main supply to the inverter with engine ON and A/C commanded. Low supply can cause sensor faults.
- With a scan tool, command the A/C compressor ON and monitor sensor B live data. Note behavior vs sensor A or expected values.
- Backprobe the sensor B connector: verify reference voltage (if present), signal voltage, and ground continuity. Check for opens/shorts to ground or battery.
- Perform a wiggle test on the wiring while monitoring live data to find intermittent faults.
Likely causes
- Damaged connector or corroded pins at the compressor/inverter connector
- Broken or shorted harness between sensor B and the inverter/control module
- Failed compressor motor voltage sensor (sensor B)
- Faulty inverter/drive electronics producing incorrect motor voltages
Fault status
Status
A/C compressor motor voltage sensor B circuit performance fault — sensor B signal out of expected range or pattern.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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