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DTC codes / P2Dxx · Hybrid propulsion / P2D43

P2D43A/C Compressor Motor Voltage B High

P2D43 indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the feedback circuit for the air conditioning (A/C) compressor motor's 'B' phase, which is one of the three electrical phases that drive the compressor. This high voltage reading typically points to an open circuit, a poor connection, or a fault inside the compressor inverter, rather than a problem with the refrigerant or the mechanical compressor itself.

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

Symptoms you may notice

  • The A/C may stop blowing cold air entirely, or it may work intermittently.
  • The climate control panel may show a flashing or steady A/C warning light.
  • The engine may idle slightly rougher or the cooling fan may run constantly as a fail-safe.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.
  • The compressor clutch may not engage, or the compressor may run at reduced capacity.
  • In some vehicles, the A/C system may default to defrost mode only.

Common causes, most likely first

  1. A damaged or disconnected wire in the compressor motor 'B' phase circuit, often due to chafing or rodent damage.
  2. Corroded or loose terminals at the compressor connector or the PCM connector.
  3. An open winding or failed internal connection inside the A/C compressor motor.
  4. A faulty compressor inverter module, which is often integrated into the compressor assembly.
  5. A PCM software glitch or internal driver fault causing a false high-voltage reading.
  6. High resistance in a ground connection shared by the compressor and the PCM.

How to diagnose and fix it

  1. Inspect the compressor motor 'B' phase wiring and connector for obvious damage, corrosion, or loose pins, and repair as needed.
  2. Measure resistance of the 'B' phase circuit from the PCM connector to the compressor connector to check for an open circuit.
  3. Check for short-to-voltage on the 'B' phase circuit with the key on and the compressor disconnected, which would indicate a wiring fault.
  4. Perform a voltage drop test on the compressor ground circuit to rule out high resistance.
  5. If wiring and connections are good, test the compressor motor windings for continuity and resistance balance across all three phases.
  6. Substitute a known-good compressor or inverter module to confirm a failed component before replacement.
  7. Reprogram or update the PCM software if a technical service bulletin (TSB) addresses this code for the specific vehicle.

Before you replace the A/C compressor

  • A high voltage on the 'B' phase often results from a simple open circuit in the wiring harness, so always perform a thorough continuity and voltage drop test before condemning the compressor.
  • Many technicians overlook a poor ground connection at the compressor mounting bracket, which can cause a false high-voltage reading on one phase.
  • This code can be set by a failing inverter module even when the compressor motor windings test good, so component-level testing is essential.
  • In some vehicles, the A/C compressor is driven by a high-voltage system, and P2D43 may be accompanied by other hybrid or electric vehicle codes that should be diagnosed first.
  • A intermittent fault may only appear when the compressor is hot or under load, so wiggle-test the harness while monitoring live data.

Can I keep driving with P2D43?

You can usually continue driving with this code because the A/C system will be disabled and the engine will not be damaged, but avoid using the A/C until the fault is repaired to prevent further electrical damage. If the code is accompanied by overheating or charging system warnings, stop driving and seek professional diagnosis.

Tools that help

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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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