P3000 — Battery Control System (Toyota / Lexus)

What it means in plain English

A battery control fault that always carries a sub-code. The sub-code names the failure; P3000 alone names nothing.

P3000 is a Toyota and Lexus code indicating a fault in the battery control system. On its own it's broad — the useful detail is in the sub-code (often called an INF code) stored alongside it, which narrows the fault down considerably. A scan tool that reads only P3000 without the sub-code has given you half the information.

Which Toyota and Lexus models this applies to

Toyota and Lexus hybrid vehicles, commonly seen across the Prius family and other Toyota/Lexus hybrids.

Possible causes

Plural on purpose. Any of these can produce this result — which is exactly why a code is not a diagnosis.

• A fault within the high-voltage battery pack itself, including a weak block.
• Battery ECU or its wiring and connectors.
• Sensor faults — voltage sensing, current sensing or temperature sensing within the pack.
• Battery cooling system faults, depending on the sub-code stored.
• Interlock or high-voltage circuit issues.
• Poor connections at the service plug or main HV connectors.

What a professional diagnostic process should check

1. 1Retrieve the sub-code, not just P3000 — this requires a scan tool with proper Toyota/Lexus hybrid coverage.
2. 2On sub-code 123, read and diagnose the HV battery ECU's own codes. Toyota's Tech Tip T-TT-0303-14 instructs technicians not to diagnose P3000/123 itself, because it records the state of the hybrid system at the moment the battery ECU set a code rather than reporting a fault of its own.
3. 3On sub-code 125, treat it as a blown high-voltage fuse and establish what blew it before replacing it.
4. 4On sub-code 388, establish why the pack discharged — Prius service material describes this code as the HV battery charge becoming low, which can follow the car being left in Neutral or running out of fuel — rather than assuming the pack is worn out.
5. 5Use the sub-code to direct the diagnosis rather than assuming a pack failure.
6. 6Capture block-level battery data under load.
7. 7Inspect HV connectors, service plug seating and interlock circuit.
8. 8Check cooling fan operation and airflow.
9. 9Verify sensor readings for plausibility across the pack.
10. 10Test the 12V battery and charging voltage.

When towing or urgent service is appropriate

Depends on how the car is behaving. Normal driving with the code stored usually allows a prompt trip to a shop; reduced power, refusal to enter READY, or additional serious faults means tow it.

Not sure which category you're in? Call 833-995-7966 and describe what the car is doing. That call is free and it might save you a tow — or a much bigger repair.