P0EA9: A/C Compressor Motor Voltage Sensor B Circuit Performance

P0EA9 means the B voltage reading reported by the electric A/C compressor looks electrically valid but does not fit other information, usually the high voltage reported by the battery system that feeds the compressor directly. No manufacturer documents P0EA9 publicly. The matching check on sensor A (P0D69) shows typical limits: Mitsubishi's 2019 Outlander PHEV flags a gap of 20 V or more lasting 2 s once the compressor sees 205 to 415 V, the battery is above 15 °C and intake air above 0 °C; GM's 2011 Volt uses more than 15 V in 35 of 40 samples. Mitsubishi names the data bus, the compressor assembly and the hybrid ECU as causes, and a drifting measurement inside the compressor is just as likely for channel B. Hard circuit faults of sensor B are P0EA8, P0EAA and P0EAB.

Symptoms

• Air conditioning switches off or works only now and then
• Fault often recorded without any other symptom

Most likely causes

• Drifting voltage measurement inside the compressor module
• Faulty data exchange between compressor and hybrid controller
• Wrong battery voltage reference from the hybrid or battery controller

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the sensor pressure in live data
2. Compare the reading with other engine data while varying the engine speed.
3. Check the relay and connector
4. Have the refrigerant charge and any leaks checked at a repair shop authorized to handle refrigerant

What each character of P0EA9 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• E: Subsystem depends on the code range
• A9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0EA9?

Yes, you can keep driving. The air conditioning may not work.

What causes code P0EA9?

The most common causes are: drifting voltage measurement inside the compressor module; faulty data exchange between compressor and hybrid controller; wrong battery voltage reference from the hybrid or battery controller.

Related codes

• P0EA8A/C Compressor Motor Voltage Sensor B Circuit
• P0EAAA/C Compressor Motor Voltage Sensor B Circuit High
• P0EABA/C Compressor Motor Voltage Sensor B Circuit Low
• P0D69A/C Compressor Motor Voltage Sensor A Performance
• P2D41A/C Compressor Motor Voltage B Performance

Sources

• mitsubishitechinfo.com: M155403150001600USA
• gsi.ext.gm.com: 11OBDG01 HYBRID Diagnostics
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.