So I have a gen 3 Prius that I just rebuilt battery on. I'm getting an error code randomly at p0b74. I can reset and we'll take sometimes hundreds of miles to come back on. Weird thing is I'm getting zero volts and up to 74 volts on. These readings are very short-lived less than a second. I don't know what it's causing the spikes or drops. A highly doubt the battery is actually reaching these voltages. I believe it is either smart battery indicator reading wrong or improper signals. Any ideas has anyone else ever experienced this. I Have checkes to make sure that all the battery terminals are tight etc. And I don't see any loose control wires.
Fairly sure I've not seen that code before. But I can tell you that the most common Prius problem related to this symptom is corrosion in the voltage sensing harness, especially in the plug socket where it connects to the ECU. So have a look at that plug and clean the pins on it... In some cases the corrosion gets so bad that it fries the plug and the battery ECU, but a used ECU is only $50 and a new voltage sensing harness (Wire Frame No. 2) is $50 as well... I've also seen terminals break on that harness which leads to warning lights and intermittent problems with voltage readings.
Okay I will give all of that a try and report back, when you say ECU you're talking about the smart battery unit attached to the actual HV battery correct? 99 percent of the time the readings are perfect between .1 .2 volts of each block
Sorry for the late reply turns out there was a bolt loose on one of the battery terminals, I believe the voltage readings were actually from a bad OBD2 adapter.
