OBD-II Code P3006
HV Battery Module Voltage Unbalance
P3006 is a more specific HV battery code than P0A80 — it indicates that the Toyota BMS has detected an unacceptable voltage difference between individual battery modules within the pack. In a healthy NiMH hybrid battery, all 28 modules should be within approximately 0.5V of each other at any given state of charge. When one or more modules drop significantly below the others (typically 1V or more of divergence), the BMS stores P3006 to flag the imbalance. This code is particularly common in Gen 1 Prius (2004–2009) where the original battery chemistry is now 15–20 years old and module-level degradation is widespread. P3006 often precedes P0A80 by 10,000–30,000 km as the imbalance worsens.
At a Glance
Fault Code
P3006
Affects
Prius Gen 1 (2004–2009) — most common, Prius Gen 2 (2010–2015), Camry Hybrid (2007–2017), Lexus CT 200h
Can You Drive?
Drive with caution
Typical Cost (BC)
$1,099–$1,399 (most common in Prius Gen 1 and CT 200h)
What Causes P3006?
- 1Individual NiMH module cells losing capacity at a faster rate than surrounding modules
- 2Thermal gradients within the battery pack causing uneven ageing (modules near cooling vents last longer)
- 3Age-related cell memory effect in original NiMH chemistry
- 4Previous deep discharge event affecting specific modules more than others
- 5Gen 1 Prius battery pack age — original packs 15–20 years old in 2024/2025
Symptoms You May Notice
- Hybrid battery warning light and red triangle
- VSC system warning simultaneously
- Noticeably reduced fuel economy
- Battery charge gauge showing unusual patterns — may charge quickly then drop suddenly
- Vehicle may enter limp mode when the weak module is under load
Can You Drive with P3006? — Drive with caution
Similar to P0A80 — the vehicle enters a protective mode but remains driveable short-term. The primary concern with P3006 is that the unbalanced module creates a bottleneck for the entire pack: the weakest module limits the overall charge and discharge capability, causing the vehicle to cut electric assist earlier and more frequently. Continued driving won't dramatically accelerate the issue in the short term but should be addressed within a few weeks.
How It's Diagnosed
- 1
Toyota-specific scan to confirm P3006 and identify accompanying codes
- 2
Module-by-module voltage testing across all 28 cells to identify the unbalanced module(s)
- 3
State-of-charge analysis to confirm which specific modules are diverging
- 4
Thermal assessment — identify if uneven cooling is contributing to uneven degradation
How It's Fixed
P3006 is best addressed with full pack replacement because the imbalanced modules are a symptom of general pack age, not an isolated failure. Replacing only the weakest modules is technically possible but typically uneconomical — the surrounding modules are of similar age and condition and will develop their own voltage divergence soon after. A fresh remanufactured pack ensures all modules are balanced and tested to identical standards.
Typical cost in BC
$1,099–$1,399 (most common in Prius Gen 1 and CT 200h)
Prices include parts and labour. Contact us for a firm quote on your specific vehicle.
Vehicles Affected by P3006
Frequently Asked Questions — P3006
At $1,099, yes in most cases. The Gen 1 Prius engine is extremely durable — many run well past 400,000 km. At our pricing, the battery cost represents far less than the cost of a replacement vehicle and extends the life of an already well-amortised car. We recommend a quick overall vehicle inspection before proceeding, just to ensure nothing else is about to fail.
The 28 NiMH modules in a Prius battery must remain within a tight voltage range of each other for the battery system to function correctly. When one module diverges significantly — 1V or more below the others — the battery management system can't effectively manage charge and discharge. The weak module hits its low-voltage limit before the rest, cutting off electric assist, and hits its high-voltage limit before the rest during charging, limiting how much charge the pack can accept. The result is a battery that behaves as if it's much smaller than it is.
Related Fault Codes
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View code guide P0A7FHybrid Battery Pack Deterioration
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View code guide P3000HV Battery Fault
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View code guideGot a P3006Code? Let's Fix It.
We diagnose and repair P3006 on Toyota and Lexus hybrids in Kelowna and across the Okanagan. Mobile service available — we can come to you.