hybrid system malfunction : ECU B No. 2 Fuse

Just an oversized fuse probably wouldn’t cause a diagnostic trouble code (DTC) to be stored.

As you may know, a fuse limits the current that can flow in a circuit. If a fuse with a higher rating is installed where one with a lower rating is needed, and the circuit is otherwise working as designed, then the fuse with the higher rating is unlikely, on its own, to cause any malfunction. Indeed, the equipment powered from the circuit generally wouldn’t be able to detect the rating of the fuse at all.

An oversized fuse doesn’t protect against an overload or fault from some other cause, though. For example, a circuit designed for a 7.5 A fuse might be wired with 0.5 mm² (similar to 20 AWG) conductors, which under some conditions can safely carry 9 A. If equipment on the circuit were to malfunction and draw, say, 23 A, then the 25 A fuse probably wouldn’t blow, but the wire would be overloaded and might melt or even start a fire.

If the person who did the electrical repairs after the collision put in fuses not only of the wrong ratings, but also of the wrong physical size—preventing the cover from being installed on the bottom of the instrument panel junction block assembly seen in your photo—I’d be concerned about what else might have been done wrong.

“Combination meter” is Toyota’s term for the instrument cluster: the pair of small displays and constellation of indicator lights under the glareshield.

That said, I think the listing of fuses and loads you shared may be for a different vehicle: on the fourth-generation Prius, the combination meter is powered from the METER-IG2, ECU-DCC NO. 2, and HAZ fuses, not the ECU-B NO.2 fuse, which powers such items as the A/C Amplifier Assembly, Radiator Shutter Sub-Assembly, Network Gateway ECU, and Hybrid Vehicle Control ECU. (For a complete list, see the interactive Electrical Wiring Diagram, available by subscription to techinfo.toyota.com.)

It wouldn’t surprise me if the current problem, which I wouldn’t ignore, even if the DTC doesn’t return immediately, stems from a faulty collision repair. With the actual DTC, we might be able to share more advice: each DTC corresponds to a section in the Repair Manual (also on techinfo.toyota.com and in the ChiltonLibrary service, to which your local public library may sponsor free access) with detailed troubleshooting information.

 

I'd agree, it's worth checking. Crash repairers sometimes do the electrical connections themselves. The only problem I've ever had after panel repairs has been electrical - though all were to do with connections of lights or indicators.

Usually more a problem with older cars. Several older cars I bought (cheap, one a project car, others for the kid's College cars), I ended up discovering a few appeared to have just had random fuses inserted - which I corrected.

 

I’d suggest reading through the diagnostic procedure for DTC P0AA649 in the Repair Manual, available by subscription to techinfo.toyota.com. There are two versions of the procedure, one for NiMH (ZVW50) and one for Li-ion (ZVW51) models. Neither version describes any INF codes for DTC P0AA649, “Hybrid/EV Battery Voltage System Isolation Internal Electronic Failure,” for which the detection condition is “Insulation resistance between the high-voltage circuit and the body has decreased.” There is a fairly long list of possible trouble areas, including—among others—the A/C compressor and its high-voltage wiring.

If you’re inclined to do your own troubleshooting, you’ll probably need a Toyota Techstream diagnostic system (or equivalent), a megohmmeter, and appropriate personal protective equipment. See the warnings in the Repair Manual, which also gives hints like “When measuring insulation resistance using a megohmmeter, measure the resistance while jiggling the high voltage wire harness.”

The text and illustrations from the Repair Manual are also available in the ChiltonLibrary service, to which the Los Angeles Public Library sponsors free access for anyone with a library card.

 

From your photo, this is a 5a fuse, not 7.5a.

 

For a 2016, why didn’t you go to a Toyota dealer first?

Some additional questions:

• What shop did you use?
• Was this the same shop as the hybrid mechanic used previously?
• Wouldn’t this be under warranty?
• How many miles on your 2016?
• How do you know they put your exact battery back in?
• Did you look at the pack they put in?

Something doesn’t seem right.

Good luck and keep us posted .

 

You’ll have to pop the lid and look at the modules to know for sure.

Each module has a unique code and knowing how to read those codes will let you know if everything is on the up and up.

Since the car is salvaged, warranties are out the window, so making sure everything is right would be what I would investigate .

Good luck .

 

Here’s a thread to review:

Is there a way to determine if HV battery is the original?

Know there are ways to know if the pack has been tampered with .

If the mechanic knew you were a salvaged car, he might have worked that to his advantage .

But more information will help.