Is there a way to test HV Battery ECU?

reread the first couple posts. if no one can help you, try techinfo.toyota.com

 

Based on a few years of reading various threads concerning hybrid battery issues on this forum, I would guess that a diagnosis of a bad battery ECU would be a "last resort" diagnosis when every other possible cause of a particular issue has been investigated and ruled out. My reason for coming to that conclusion is that any tool that you will use to diagnose the battery, other than direct measurement of voltages and capacities on individual modules, depends on communication with the ECU. If a journalist suspects a source is lying to him, what does he do? He might look for another source to corroborate what he was being told, but may not be able to find one. The battery ECU is really our only source of information about the battery. Possibly you could measure the voltage of a particular module with a multi-meter and compare it to what the ECU was reporting to Techstream at that precise moment, but even if you could do that for all 28 modules, I suspect there are other factors that could create differences in measurement, and there are undoubtedly other tasks that the ECU must perform that you would have no way of evaluating.

All that being said, there are specific codes the presence of which might lead you to suspect a bad battery ECU. I believe they might be found on the following list, but that is just a guess. Others members of this forum might have others to add, or some that should be removed from the list.

P0A1F Battery Energy Control Module
P0A7F Hybrid Battery Pack Deterioration
P0A80 Replace Hybrid Battery Pack
P0A82 Hybrid Battery Pack Cooling Fan 1
P0A84 Hybrid Battery Pack Cooling Fan 1
P0A85 Hybrid Battery Pack Cooling Fan 1
P0A95 High Voltage Fuse
P0A9C Hybrid Battery Temperature Sensor "A"
P0A9D Hybrid Battery Temperature Sensor "A" Circuit Low
P0A9E Hybrid Battery Temperature Sensor "A" Circuit High
P0AAC Hybrid Battery Pack Air Temperature Sensor "A" Circuit
P0ABF Hybrid Battery Pack Current Sensor Circuit
P0AC0 Hybrid Battery Pack Current Sensor Circuit Range/Performance
P0AC1 Hybrid Battery Pack Current Sensor Circuit Low
P0AC2 Hybrid Battery Pack Current Sensor Circuit High
P0AFA Hybrid Battery System Voltage Low

 

I was thinking about this and found the following diagram in the Repair Manual that furthered my understanding of the battery ECU and might do the same for you.

 

I do not recollect anyone sharing a method to check the ECU. Usually, where there is reason to believe the ECU is faulty, people just buy a second-hand one to replace it – they are relatively cheap. In the absence of physical damage at the connector, these ECUs are pretty reliable, so it would be a last resort to change it out.

 

Yep. A second hand one is relatively inexpensive.
Swap out with a known good doesn't take much time.

 

Just curious, if you are still connected 5 years later, were you experiencing any other symptoms besides that scary RED TRIANGLE?

Thanks for your attention.