P3011–P3029: Battery Block Becomes Weak
Find Out Exactly Which Part of Your Toyota or Lexus Hybrid Battery Is Failing
✓ Toyota Prius (2001–2009) and related Toyota/Lexus hybrids
✓ Block-to-module location table
✓ Mobile testing by DFW Hybrid Battery — we come to you
Quick Answer
Official definition: P3011 through P3029 — “Battery Block [1–19] Becomes Weak.”
What triggers it: The battery computer finds abnormal internal resistance or voltage in one specific block (a pair of modules).
Detection: One-trip detection — the light comes on the first time the fault is seen.
Most common on: 2004–2009 Prius (P3011–P3024, 14 blocks), 2001–2003 Prius (up to P3029, 19 blocks), and other early Toyota/Lexus hybrids.
Good news: These codes point to a location, which makes targeted module repair possible.
Unlike many hybrid codes, the P3011–P3029 group is very specific: each code number points to one battery block. On the 2004–2009 Prius that is a pair of modules out of 28. Toyota’s manual says the computer flags a block for abnormal internal resistance or electromotive voltage, and the monitor runs continuously. The light comes on immediately after the first detection.
Code-to-Block Table (2004–2009 Prius)
| Code | Block | Module pair |
|---|---|---|
| P3011 | Block 1 | Modules 1 and 2 |
| P3012 | Block 2 | Modules 3 and 4 |
| P3013 | Block 3 | Modules 5 and 6 |
| P3014 | Block 4 | Modules 7 and 8 |
| P3015 | Block 5 | Modules 9 and 10 |
| P3016 | Block 6 | Modules 11 and 12 |
| P3017 | Block 7 | Modules 13 and 14 |
| P3018 | Block 8 | Modules 15 and 16 |
| P3019 | Block 9 | Modules 17 and 18 |
| P3020 | Block 10 | Modules 19 and 20 |
| P3021 | Block 11 | Modules 21 and 22 |
| P3022 | Block 12 | Modules 23 and 24 |
| P3023 | Block 13 | Modules 25 and 26 |
| P3024 | Block 14 | Modules 27 and 28 |
On the 2004–2009 Prius, block 1 is at the end of the battery farthest from the battery ECU (passenger side). On the 2001–2003 Prius the numbering starts at the other end, near the ECU. Counting from the negative end, the voltage increases with each block. A technician will confirm the location by measuring the modules rather than relying on the code alone.
Other Vehicles
| Vehicle | Blocks / codes | Confidence |
|---|---|---|
| 2001–2003 Prius (Gen 1) | 19 blocks — P3011 to P3029 | Technical reference (ecrostech) |
| 2004–2009 Prius (Gen 2) | 14 blocks — P3011 to P3024 | Toyota repair manual |
| 2007–2011 Camry Hybrid | Reported by technicians as 34 modules / 17 blocks — up to P3027 | Technician forums (not factory-confirmed) |
| Highlander Hybrid / Lexus RX 400h | Sources disagree on block count | Confirm on the vehicle |
Because sources disagree on some larger SUVs, we never pull a module based on a code number alone. We measure.
Why the Middle Blocks Fail First
Repair technicians commonly see weak-block codes in the center of the pack. The middle modules are surrounded by other modules, so they run warmer and age faster. In Texas, where cabin and trunk temperatures stay high for months, a clogged cooling fan makes that heat even worse. See our battery cooling codes guide for the fan side of the story.
How a Weak Block Is Confirmed
- Read all stored codes — a weak-block code usually appears with P0A80 and P3000.
- Compare block voltages under load. The weak block drops away from the others.
- With the pack safely removed, measure each module. A common technician rule of thumb: after resting about 24 hours, a module more than about 0.05 V below the highest is suspect.
- Capacity-test suspect modules before deciding on repair or replacement.
Repair: Replace Two Modules or the Whole Pack?
Because the code names one block, it’s tempting to replace just two modules. That can work well when the rest of the pack tests healthy and the replacements are matched. But if neighboring modules are also close to failing, a different block code can appear weeks later. Technician forums include reports of weak-block codes returning after reconditioning. That’s why we test the whole pack and give you an honest view of how many modules are near the edge.
How DFW Hybrid Battery Handles This Code
We come to you, read the exact block code, confirm it with load testing, and measure the modules. You’ll see the data and get options: targeted module repair, full reconditioning, or replacement — with the pros and cons of each for your car.
Frequently Asked Questions
If I have P3018, are only two modules bad?
Block 8 is the weakest right now, but other modules may be close behind. Whole-pack testing tells you whether a two-module repair will last.
Can I drive with a weak-block code?
Usually for short trips, with reduced fuel economy and power. Over time, the weak block can lead to a no-start.
Do newer Toyotas use these codes?
Later models report battery problems differently (for example seven-character codes such as P1AC000), so P3011–P3029 is mainly seen on earlier hybrids.
Related Hybrid Codes
- P0A80 — block imbalance
- P3000 — battery control system messenger code
- P0AFA / P0B3B–P0B83 — voltage-sense circuit problems
- All hybrid battery error codes
Vehicle guides: Toyota Prius Gen 2 · Lexus RX400h & RX450h · All vehicles
Related services: Hybrid Battery Diagnostics · Repair & Reconditioning · Replacement · Warranty · Battery Charging · Prices · Areas We Serve
Sources & References
We base these guides on factory service bulletins, repair-manual information, and what we see in real repairs. Where a detail comes from technician forums or a parts seller rather than the manufacturer, we say so.
- Toyota repair manual excerpt: P3011–P3024 Battery Block Becomes Weak (2004 Prius)
- Ecrostech: Gen1 Prius battery ECU DTCs
- PriusChat: block numbering by generation
- Import Car: Toyota Prius battery codes P0A7F, P3011 and P0A80
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