power management control ECU needs to be replaced?

sounds like a bad battery

 

What year is your prius, and how many miles? Also if you haven't maybe try disconnecting the 12 volt battery and see if that helps. Never heard of these problems from a prius before

 

i think (hope) it is your 12v. jumping doesn't always work with a bad 12v, and 12+ volts sounds low.

how many miles on her? is it the original battery?

idk who wrench mobile mechanic is, but she sounds clueless.

 

The Power Management Control ECU is the main computer for the hybrid system. It’s the module behind the glove compartment labeled 89681A in this image from Figure 84-01, Switch & Relay & Computer, in the parts catalog. Toyota’s list price for a new one is $678, but a dealer near me sells them online for $468.

None of us has seen the car, so it’s difficult to confirm or refute the diagnosis you’ve been given. Did the mechanic say anything about how he determined that the Power Management Control ECU was the faulty part?

The Power Management Control ECU has an important role in the shift control system, but in general, ECUs themselves are the least likely parts to fail: it’s more common for the trouble to be in wires, connectors, or sensors and actuators. The computers have extensive self-diagnostic capabilities; were any warning lights displayed when you tried to shift to neutral?

Did the mechanic use a Toyota Techstream diagnostic system, or equivalent, to check for diagnostic trouble codes? If the mechanic works on all kinds of cars, he might have had only a generic scan tool made for engine and emissions diagnosis, which wouldn’t have been able to communicate with hybrid-specific computers like the Power Management Control ECU.

The Power Management Control ECU also doesn’t have much to do with the headlights, especially if the problem is only on one side. If the fuses and lamps (bulbs) are OK, headlight trouble is more likely to be a problem with a wire, connector, lamp socket, or relay, or perhaps—but less likely—with a different computer, the Main Body ECU, which handles several miscellaneous functions.

When there are problems with unrelated systems, I’d look for a common cause, like a damaged wiring harness. Several PriusChat members have reported trouble from rodents gnawing on the wires, who of course don’t take care to damage only one system at a time. Another possibility is that a connector or fuse was disturbed during your troubleshooting for the headlight problem.

Maybe the operator was concerned about damaging your car or surrounding structures, but a good towing service should be able to extract a car from just about anywhere, regardless of its condition, by putting dollies under the wheels, if necessary. If the tow truck was dispatched by an auto club or roadside assistance plan, perhaps they don’t pay for this extra labor. I’d try calling other towing companies before giving up.

I assume it’s getwrench.com.

 

That’s possible, but the connectors are locking types that are designed not to come out inadvertently.

If that master warning light is on, there should be one or more diagnostic trouble codes (DTCs)—each a letter (B, C, P, or U) followed by four or more digits or letters—stored in the car’s computers. Every DTC has a specific troubleshooting procedure in the Repair Manual, available by subscription to techinfo.toyota.com or through the ChiltonLibrary service from public libraries (such as SPL or KCLS).

I wouldn’t be inclined to replace an ECU, especially at that cost, without knowing which DTC or DTCs are present and that the appropriate diagnostic steps from the Repair Manual have been done to confirm the cause of the trouble. The dealer should do this, as would a competent independent shop.

It’s disappointing that the mobile mechanic didn’t give you more information, though. It might be worthwhile to have a different mobile mechanic—preferably one that has a Toyota Techstream system and knows how to use it—attempt to diagnose the car, especially if having it towed would be costly or impractical.

 

good call.

 

I’m more surprised the original battery lasted this long, mine gave out in 4-5 years.

 

My original lasted 8.5 years .

Would’ve lasted longer, but I got 12.3 volts after sitting overnight and figured I wouldn’t tempt fate any further.