Honda B2989 – A/C Compressor Motor Problem

Honda-specific code — factory diagnostic data

Last updated: May 6, 2026

Definition source: Honda factory description. Diagnostic guidance is based on factory-defined fault logic for this code.

B2989 sets when the climate control module or compressor inverter sees a fault inside the electric A/C compressor motor itself — winding open, winding short, internal driver fault, or position-feedback failure. On hybrid models the compressor is electrically driven from a high-voltage source so the cabin can be cooled with the engine off. The system shuts the compressor down when the code sets and disables A/C output until the fault is repaired.

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B2989 Quick Answer

On a Honda hybrid, B2989 means the electric A/C compressor reports an internal motor fault. The most common causes are an internally failed compressor motor, a damaged compressor inverter (built into the compressor on most platforms), or a high-voltage harness fault between the IPU and compressor. A/C cooling will be unavailable until the fault is repaired. Diagnosis and repair require high-voltage safety procedures.

The Diagnostic Procedure

This procedure is for trained technicians familiar with hybrid high-voltage safety. You will need a scan tool that communicates with the climate control module and the hybrid powertrain (Honda HDS recommended), the appropriate insulated PPE (Class 0 gloves rated for the system voltage), the vehicle’s high-voltage shutdown procedure documented for your specific model, a megohmmeter for insulation testing, and the model-specific service manual.

1. Confirm B2989 and check for any high-voltage related codes (insulation faults, IPU faults, MCM faults). If insulation or HV-bus codes are stored, treat the high-voltage system as unsafe to work on until those faults are resolved.
2. Read freeze frame data: was the compressor commanded on, what speed, what cabin temp, was the engine running or in EV mode? Hybrid compressors fail more often during hot soak followed by demand.
3. Visually inspect the compressor and high-voltage cable routing without removing covers — look for oil leaks, refrigerant stains, impact damage, rodent damage, and connector seating.
4. Follow the model-specific high-voltage shutdown procedure: remove the service plug, wait the prescribed time, and verify zero voltage at the compressor connector with a meter rated for the system voltage.
5. With the high-voltage system safely disabled, inspect the compressor connector for oil contamination — refrigerant oil migration into the high-voltage connector is a known Honda failure mode that shorts the windings and sets B2989.
6. Perform an insulation resistance test from each compressor phase to compressor body using a megohmmeter at the manufacturer-specified test voltage. Low insulation resistance confirms a compressor failure.
7. Measure phase-to-phase resistance with a low-resistance ohmmeter. The three windings should read within a tight tolerance of each other. A mismatch indicates an internal winding fault.
8. If electrical tests fail, replace the compressor as an assembly. The inverter is integrated into the compressor on most Honda hybrid platforms and is not a separate part.
9. After repair, follow the system evacuation, charging, and re-energising procedure from the service manual. Use only the refrigerant oil specified for high-voltage compressors — conventional PAG oil is conductive and will destroy the new compressor.
10. Clear B2989, run the system through a cooling cycle, and verify A/C output and the absence of high-voltage faults.

Common Causes

• Internal compressor motor failure: Winding insulation breakdown is the most common single cause. Often follows an oil migration event or long-term operation with low refrigerant charge.
• Refrigerant oil migration into the high-voltage connector: A known failure pattern. Oil tracks up the cable, shorts windings to body, and sets B2989. Inspect the connector at every service.
• Use of incorrect refrigerant oil: Conventional PAG oil is electrically conductive and will destroy the windings within weeks. Hybrid compressors require a non-conductive POE oil specified by Honda — never substitute.
• High-voltage cable damage: Impact, rodent damage, or chafe-through on the orange high-voltage cable from the IPU to the compressor.
• Integrated inverter electronics failure: The driver electronics built into the compressor housing fail from heat. Diagnosis is by elimination because the inverter is not separately serviceable.

Severity & Driving

B2989 does not stop the vehicle from running. The hybrid system continues to operate normally and the engine, brakes, and steering are unaffected. You will lose A/C cooling — the cabin can only be cooled by ambient air, which becomes a real comfort and safety issue in hot weather. The hybrid system may also use the A/C system for battery thermal management on some models; loss of A/C can reduce hybrid battery cooling capacity in hot weather and lead to derate codes. Have the fault inspected promptly, especially before hot weather use.