OBD-II trouble code
P324E: Toyota/Lexus: MG-ECU Power Relay Intermittent Circuit
Application matters: The archived Lexus CT200h RM1720E entry is P324E-788, MG-ECU Power Relay Intermittent Circuit. Toyota’s separate Prius/Prius V bulletin lists P324E but requires its own vehicle, inverter-type and information-code assessment; the Lexus circuit layout is not a Prius instruction.
The cited Lexus description concerns a reset of inverter electronics caused by a power-source problem. The relay wording does not by itself identify an external relay or authorize inverter replacement.
Quick facts
- System
- Powertrain
- Category
- Hybrid Propulsion
- Severity
- High severity
- Driving guidance
- Stop safely and arrange diagnosis
- Repair cost range
- Get a vehicle-specific estimate after diagnosis.
- DIY difficulty
- Shop recommended
A code alone cannot establish whether driving is safe. Stop safely for a red brake or oil-pressure warning, overheating, severe misfire, stalling, or impaired braking or steering, and follow the owner's manual. Restraints faults can reduce crash protection even when the vehicle runs normally.
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What does P324E mean?
The cited Lexus CT200h entry names P324E-788 MG-ECU Power Relay Intermittent Circuit. It explains that the power management control ECU records the fault when inverter electronics reset because of an inverter power-source problem. Its detection table concerns an error in the reset signal from the inverter assembly power-source IC.
That description does not establish a failed external relay. The Lexus trouble-area list includes the harness or connectors, inverter with converter assembly, engine-room junction block and power management control ECU. Those are alternatives for diagnosis, not a cause ranking or a parts list to replace together.
The complete scan can also change the diagnostic route. The Lexus procedure distinguishes P324E-788 alone from a report with specified U0110 information codes, then uses connection and circuit findings in its conditional checks. Preserve all module faults and detail codes. A currently absent symptom does not establish that the power source, connection or electronics are healthy.
Toyota T-SB-0003-21 Rev1, revised February 16, 2023, separately covers some 2010–2015 Prius and 2012–2017 Prius V vehicles with P324E among its listed codes. The specified physical-damage finding leads to an assembly branch; without that damage, selection depends on inverter type, DTC and information code. Neither the Lexus title nor the Prius bulletin supports choosing a relay, module or complete inverter from P324E alone.
This is qualified hybrid-system work. Do not swap relays, disconnect inverter connectors, probe terminals or use resets and repeated starts to reproduce the condition. High-voltage access requires the complete current manufacturer isolation, waiting and verification process. Observe actual stop warnings and obtain assistance for unavailable READY or unreliable propulsion.
Possible causes
- A power-supply wiring or connector fault demonstrated by the matched circuit checks
- A junction-block or power-management control concern established by the vehicle diagnosis
- An inverter-associated power-source or electronic fault confirmed after the applicable diagnostic branches
Symptoms
- P324E with an information code in a hybrid-system scan
- A malfunction indicator or hybrid warning on a matching application
- An intermittent operating complaint or READY concern whose cause must be established
Diagnostic steps
Save the full scan report, code status, and available freeze-frame data before clearing anything. Confirm the reporting module, any failure-type suffix, and the procedure for the exact vehicle. The steps below are an overview; use manufacturer specifications and safety procedures for testing.
- 1.Save the complete scan, available information codes, current/history status, event data and actual warnings before clearing.
- 2.Have qualified personnel match the vehicle and reporting controller to the correct reset/power-source diagnosis.
- 3.Include companion module faults when selecting the diagnostic branch; one base code is not enough to condemn a relay or inverter.
- 4.Keep connector access, protected circuit tests and any required component work within the full manufacturer procedure. Do not substitute a relay swap or a generic terminal test.
- 5.Request confirmation of the established repair and original complaint. Follow warning and recovery instructions rather than clearing the code to judge whether a trip is safe.
Repair cost
Get a vehicle-specific estimate after diagnosis.
A trouble code alone does not price the repair. Ask the shop to identify the confirmed fault and itemize diagnosis, parts, labor, programming or calibration, and taxes.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with hybrid-system fault diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
Related repairs
These links are planning examples; the code does not confirm that any listed part has failed.
DIY vs shop
A qualified shop is recommended because this can involve a high-voltage traction system that stays live with the car switched off and requires documented shutdown procedures, in-date insulating gloves, and specific training. Ask the technician what testing confirmed the repair.