A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
Possible causes
- A fault in the HV battery ECU — its exact code is stored in that unit
- High-voltage battery, inverter or their wiring
- The 12 V battery: low voltage
What you can do yourself
- This is a general code: the hybrid ECU stores it when the battery ECU has found a fault. The battery ECU’s codes show the cause — read them with a scan tool.
- Check the 12 V battery: on a hybrid the whole system relies on it to start.
- Don’t touch the high-voltage parts (orange cables) — they are life-threatening.
- High-voltage repairs are for a hybrid specialist only.
Stop and don’t drive on if:
- The Check Engine light is flashing
- The temperature gauge is in the red or the overheating light is on
- The red oil pressure light is on
- Smoke from under the bonnet, a burning or petrol smell
- Strong jerking, knocking from the engine, or the car barely moves
OOleg’s tip: check the connector
Often the cause is simple — there is no contact in the connector (plug). Look at the connector from the back: remove the rubber seal and you will see whether a wire is corroded or has come off completely. Corrosion shows up as green deposits. Ideally, gently pull each wire towards you one at a time: a sound wire stays in place, while a corroded one simply comes off — it needs to be repaired.
Unplug and inspect connectors with the ignition off.
A Toyota and Lexus hybrid code. This is the Toyota and Lexus meaning. On other makes this number means something else: if your car isn’t a Toyota or Lexus, change the make at the top.
Source: Toyota T-TT-0303-14 (static.nhtsa.gov), prius.ecrostech.com
The explanation comes from the error code reference in the AvtoElektrik PRO app.