P324E on Toyota: How to Diagnose & Fix
MG ECU Power Relay Intermittent Circuit
1 Toyota model · 1 documented issue · 1 critical · $2,500-$5,000 repair
P324E on Toyota by model: symptoms, diagnosis and fix
Transistors inside the Intelligent Power Module of the inverter/converter assembly can overheat and fail under sustained high load (long grades, hard acceleration, hot weather). When the module faults, the hybrid system shuts down and the car can stall at speed, sometimes without warning. Toyota first issued a software recall to reduce IPM thermal stress (NHTSA 14V-053, ~701,000 US Gen 3 cars), later expanded remedies (18V-684), and created Customer Support Program ZE3 extending inverter coverage on 2010-2014 Prius to 15 years/unlimited miles. Owners report stalls persisting after the software remedy, which drove follow-on litigation. This is failure of the inverter itself - distinct from the inverter coolant pump.
Common Symptoms
- Vehicle stalls or loses power at highway speed
- Red triangle hybrid warning and check engine light
- Limp-home / reduced power mode
- Car will not restart until cooled or after a reset
- Burning smell from under the hood in severe cases
How to Fix
Verify the recall/CSP status by VIN at the NHTSA or Toyota owners site and have the software remedy applied if outstanding. If the IPM has actually failed, the fix is replacement of the inverter/converter assembly (Toyota does not sell the IPM separately), followed by a full inverter coolant fill and air bleed - and the inverter coolant pump should be checked at the same time, because a weak pump is a common contributor to IPM overheating. Push for ZE3 coverage on 2010-2014 cars before paying out of pocket.
Sources for this issue (3)
P324E code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P324E mean on a Toyota?
P324E stands for "MG ECU Power Relay Intermittent Circuit." The MG ECU, which lives inside the inverter with converter assembly and controls the motor-generators, lost and regained its power source. When the MG ECU resets because of a problem with the power supply inside the inverter, the power management control ECU records P324E. It is an intermittent power-supply fault, not a motor fault. Toyota bulletin T-SB-0036-16 lists P324E (sub-code 788) alongside P0A94, P0A1A, and P3004 as inverter-assembly malfunctions on 2010-2014 Prius and 2012-2014 Prius v, and the prescribed repair for the P324E path is replacement of the IPM transistor and the MG ECU. Toyota's later IPM programs extend coverage where the IPM failed from a thermal event. On Toyota it is documented across 1 model: Prius.
What are the most common causes of P324E?
The most common causes of P324E are: Intelligent Power Module (IPM) failure inside the inverter, often thermally induced, MG ECU (MG control computer sub-assembly) internal fault, Loss or interruption of the MG ECU power supply inside the inverter with converter assembly, Inverter internal connector or solder-joint degradation. The specific cause varies by vehicle.
How much does it cost to fix P324E on a Toyota?
Published repair estimates on Toyota range from $2,500 to $5,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P324E on a different make?
View P324E across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.