We had a Honda Civic Hybrid come in with an IMA warning light and a 12V battery that kept going dead. Unfortunately for our customer, he had two separate issues. First, the car would no longer power up at all after a jump start. The car had been jumped backwards and blown the 100A main fuse. Before calling the customer with an estimate, we installed a jumper to by-pass the fuse and see if there were any other problems. Frequently when a Prius is jumped backward, the DC-DC converter will be damaged, so it made sense to check this Civic before calling.
It was a good thing we checked because the IMA light was on, and the DC-DC converter had no output and P0AE1 set. When checking techinfo.honda.com, we found a related TSB.
The TSB said the following:
The Motor Power Inverter (MPI), also known as the Intelligent Inverter Unit (IIU), may fail over time due to a defective
solder joint. This failure may result in one or more of the following DTC(s):
P1440 (MPI Module Output Circuit Malfunction)
P1437 (MPI Module Short Circuit)
P15A5 (Motor Current Sensor Circuit Malfunction)
P0A78 (MPI Module Internal Circuit Malfunction)
P0AE1 (Bypass Contractor Malfunction)
P0A3C (Motor Control Module (MCM) Overheating)
P0A3F (Motor Rotor Position Sensor Circuit Malfunction)
P0DA8 (MPI Module Voltage Malfunction)
P1634 (MPI Module Signal Circuit Malfunction)
P0AEE (MPI Internal Circuit Malfunction)
P0A27 (High Voltage Contactor Stays Activated)
American Honda is extending the warranty coverage of the motor power inverter (MPI) on these vehicles to 15 years from
the original date of purchase or 150,000 miles, whichever comes first.
P0AE1 isn’t covered for this customer
Honda said our customer’s P0A01 doesn’t qualify for warranty coverage since his car has 160K miles. The part (061B0-RW0-A00) isn’t crazily expensive – $896 at the time of this writing. As it turned out, the MPI we removed from the car was a used part. It had an auto recycler’s marking in paint pen. The person who installed it may not have known about the warranty extension, or maybe it had happened after the 150K cut off.
The smoking gun
The TSB said the issue with the MPI is a defective solder joint. I’m very good with soldering, so I figured I might be able to fix the part and save a future customer some money. No luck. One of the IGBTs burnt out. There’s no way to fix this, so into the trash it went. However, the time I spent disassembling the MPI was still worth it. I enjoyed seeing how the IGBTs are connected and potted.