2001 Prius Code P3125 Subcode 264

Disclaimer: I only have a Gen 2 service manual. However, Toyota kept the INF codes the same even though (in this case) they changed the DTC from a Toyota-defined one (P3125) to an SAE-standard one (P0A08) on the Gen 2.

I think I said before that your best option is a couple of days' subscription to TIS and to grab the 2001 service manual. Still, I'm posting this anyway in case it helps.

The DTC is given in the newer manual as 'DC / DC Converter Status Circuit' and at Ecrostech.com (home of the 'Graham scanner') as 'DC/DC Converter Malfunction. DCDC converter malfunction'. The Gen 2 manual says:

"The HV Control ECU monitors the DC / DC converter circuit status via the NODD terminal. If the ECU detects an internal circuit malfunction in the converter and stops converter operation with its fail-safe function, causing the auxiliary battery voltage to drop below 11 V, the ECU outputs DTC P0A08 (INF 264)." (Gen 1 obviously reports P3125, not P0A08.)

The troubleshooting chart says to check for DTCs corresponding to P3115 (System Main Relay Malfunction) and P3009 (Leak Detected - from the Battery ECU, HV ECU will log P3000) on Gen 1. It also mentions P0A94 (DC/DC Converter Performance) which I can't match to a Gen 1 DTC - the INF codes mentioned are 442, 545-561, 583-585 and 597-590. If any of these DTCs are reported, you should investigate and resolve them first. (Basically they are various causes for the HV system not working, but since you can drive the car, I'm ruling most of them out - it says either 'Limited Driving', 'Impossible To Drive' or 'Normal Driving (until next switched OFF)'). Only INF codes 224 and 225 of P3115 (Gen 2: P0AE7 'Hybrid Battery Precharge
Contactor Control Circuit High', P0AE6 'Hybrid Battery Precharge
Contactor Control Circuit Low') show 'Normal Driving'. (The 'Precharge Contactor' is an extra relay which switches in a resistor when initially switching on the main relays, so that the current doesn't spike.)

Assuming none of these DTCs occurs, check the following things:

- Check that the 12V auxiliary battery terminals are securely connected.
- Check that the fusible link block is securely connected. (On Gen 2 this is mounted on top of the 12V aux battery.)
- Check that there isn't a short from the fusible link block connectors to chassis ground. (The manual says to check that the resistance is less than 1 Ohm, but that's nonsense - the fusible link carries power from the battery to the rest of the car.)
- Check that the fusible link is intact (low resistance across it). This is unlikely to have blown, the car wouldn't boot up.
- Check that the 100A DC/DC converter fuse is good. In the Gen 2 this is mounted in the main fuse box - the jump terminal is one end of it.
- Check that all terminals of the HV ECU are securely connected.

After this, the next stage involves taking off the inverter cover and disconnecting the motors, so it's not for the faint-hearted! I would definitely recommend picking up the proper service manual if you get to this stage.

I suspect there's probably a fault in the connection between the inverter and HV ECU - probably the NODD line which tells the HV ECU whether the DC/DC converter is working.

 

Hi try, please bear in mind that your first inverter failed for some reason. Perhaps the most likely is that its liquid cooling system was not working properly.

In the (top center) reservoir for that system, when the Prius is "Ready" the liquid flow inside that reservoir should appear turbulent and distinctly higher towards the front of the car. If yours is not so you must find out why and fix it.