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P1446 is a manufacturer-specific Honda powertrain code set on Honda Civic Hybrid and Accord Hybrid models equipped with the IMA (Integrated Motor Assist) system. The full description is “Battery Module Individual Voltage Input Deviation.”
Understanding what “deviation” means here is key to understanding what this code is actually telling you. Honda’s IMA battery pack is built from multiple NiMH cell modules arranged in series. In a healthy pack, all modules charge and discharge together in lockstep, their individual voltage readings stay closely matched throughout the operating range. Over time, as cells age, they begin to diverge. Some modules lose capacity faster than others, some self-discharge at different rates, and some retain charge better under different temperature conditions. When the spread between the highest-reading and lowest-reading module grows large enough to exceed Honda’s acceptable threshold, the Battery Control Module logs P1446.
This is the critical distinction from P1570: P1570 fires when a module’s absolute voltage reading is abnormal and the module itself is reading wrong. P1446 fires when the relative difference between modules is too large and the pack is no longer behaving as a balanced unit, even if individual module readings might each appear to fall somewhere within a plausible range on their own.
The misdiagnosis problem: On Nissan, Kia, Infiniti, BMW, and many other vehicles, P1446 is an EVAP system code related to the canister vent control valve — nothing to do with the battery. Shops that work on conventional vehicles and see P1446 on a Honda hybrid sometimes default to treating it as an EVAP fault, chasing vent valves and canister components that have nothing wrong with them. On Honda Civic Hybrid and Accord Hybrid, P1446 is a hybrid battery code and must be diagnosed by a specialist familiar with the IMA system.
The Honda Insight connection: On first-generation Honda Insight models, this same fault description “Battery Module Individual Voltage Input Deviation” appears as sub-code 74 under the P1449 primary code rather than as P1446 directly. The underlying condition is the same; the code structure differs by platform and model year.
WARNING BOX: P1446 should not be dismissed as a minor imbalance. A voltage deviation between modules that’s large enough to trigger a code means the pack is already operating in a significantly unbalanced state. Continued driving in this condition forces stronger modules to work harder to compensate for weaker ones, accelerating wear across the entire pack and increasing the likelihood of further degradation.
Step 1 — Full Code Scan Including Sub-Codes We pull every stored code across all modules. P1446 appearing alongside P0A7F (High Voltage Battery Capacity Serious Deterioration) is a more conclusive picture than P1446 appearing alone. Sub-codes identifying specific modules are noted and guide the physical testing sequence.
Step 2 — Misdiagnosis Check We confirm we’re treating P1446 as the Honda battery code it is not an EVAP issue. This sounds obvious but matters in mixed-fleet shops where the default P1446 interpretation points to a canister vent valve.
Step 3 — 12V Battery and Cooling Fan Check Before testing the IMA pack directly, we verify the 12V auxiliary battery is healthy and the IPU cooling fan is functioning. A failed or restricted cooling fan causes uneven thermal conditions that accelerate differential module aging and can trigger P1446 even in packs that still have reasonable overall capacity.
Step 4 — Individual Module Voltage Mapping We test each module (stick) in the IMA pack individually and map the spread across the pack. This tells us whether one or two modules are significant outliers dragging the deviation score, or whether the spread reflects broad aging across the whole pack. The answer determines whether targeted reconditioning is viable or full replacement is the right call.
Step 5 — Load and Balance Assessment We test the pack under real discharge conditions, not just at rest. A pack can appear balanced at static voltage but show significant spread under load — this is where mild-deviation cases either reveal themselves as manageable or confirm they need replacement.
Step 6 — Honest Recommendation If the deviation is driven by one or two outlier modules and the rest of the pack shows reasonable capacity, a reconditioning cycle may bring the pack back into balance — we’ll tell you that. If the spread reflects broad pack aging that reconditioning can’t fix, full IMA battery replacement is the appropriate path. You’ll get a written quote with our Unlimited Mileage Warranty before any decision is made.
P1446 as a Honda IMA battery code applies to:
Note on other vehicles: On Nissan, Infiniti, Kia, BMW, MINI, Subaru, and most other makes, P1446 means something entirely different, usually an EVAP canister vent valve fault or an emissions system issue. If you have a Honda Civic Hybrid or Accord Hybrid and see P1446, it is a battery code. If you have any other make, this page does not apply to your vehicle.
Since these three codes appear on the same Honda hybrid platform and all involve the IMA battery system, it’s worth being clear about what each one specifically flags:
P1446 — Battery Module Individual Voltage Input Deviation: The spread between individual module voltage readings has exceeded the acceptable range. A pack imbalance code about the relative difference between modules. May reflect broad aging or one dominant outlier module.
P1570 — Battery Module Individual Voltage Problem: One or more modules are reading an abnormal absolute voltage either too high, too low, or unstable on their own terms, not just relative to others. A direct module voltage fault rather than an imbalance measurement.
P1575 — MCM Voltage Malfunction / Motor Power Inverter Module Voltage Problem: The voltage interface between the IMA battery and the Motor Power Inverter module has a problem. More of an inverter-side code than a direct battery cell code, though battery degradation can be the upstream cause.
All three can appear on the same vehicle simultaneously in advanced IMA system failure.
If it’s a cooling fan issue driving uneven degradation: IPU cooling fan replacement typically runs $150-$400. Addressing this before it accelerates further cell damage is worthwhile if the pack is otherwise in reasonable shape.
If it’s the 12V auxiliary battery: $150-$300.
If reconditioning is viable (mild imbalance, no P0A7F companion code): Reconditioning or grid charging procedures at a hybrid specialist typically run $100–$300 and may restore acceptable balance in packs where the deviation hasn’t progressed too far.
If IMA battery replacement is needed: Dealer pricing for IMA battery replacement typically runs $2,000-$3,500 depending on model year. Greentec Auto offers remanufactured IMA battery replacements at significantly lower pricing with our Unlimited Mileage Warranty included. Call 1 (800) 773-6614 for a free quote on your specific Honda model and year.
Q: What does P1446 mean on a Honda hybrid? A: P1446 on a Honda Civic Hybrid or Accord Hybrid means “Battery Module Individual Voltage Input Deviation.” The Battery Control Module has detected that individual modules inside the IMA battery pack have diverged significantly from each other in voltage — a cell imbalance condition indicating the pack is no longer operating as a balanced unit.
Q: How is P1446 different from P1570? A: P1570 flags an abnormal absolute voltage in a specific module that module is reading wrong on its own. P1446 flags a deviation between modules — some are reading noticeably higher or lower than others, meaning the pack has become imbalanced. P1570 is a single-module fault; P1446 is a pack-balance fault. Both point toward IMA battery issues but describe different aspects of degradation.
Q: Why does my mechanic think P1446 is an EVAP code? A: Because on almost every other vehicle, it is. On Nissan, Kia, BMW, Infiniti, and most conventional vehicles, P1446 means an EVAP canister vent control valve fault. On Honda Civic Hybrid and Accord Hybrid specifically, Honda used the same code number for a completely different fault — Battery Module Individual Voltage Input Deviation. A shop without Honda hybrid expertise will default to the more common EVAP interpretation. This is one of the most common P1446 misdiagnoses in the Honda hybrid world.
Q: Can the imbalance be fixed without replacing the battery? A: In mild cases where the deviation is being driven by one or two outlier modules and the rest of the pack retains reasonable capacity, reconditioning or grid charging procedures can sometimes bring the pack back into acceptable balance. In cases where the spread reflects broad aging across the pack — especially if P0A7F appears alongside P1446 — reconditioning is unlikely to provide a lasting fix and full replacement is the appropriate path.
Q: Is P1446 dangerous to drive with? A: The car will usually still run, but the IMA system is operating with a significantly compromised pack. Continued driving in this state forces healthy modules to compensate for weaker ones, accelerating overall pack degradation. The sooner it’s addressed, the better the outcome, both for the pack and for fuel economy in the meantime.
Q: Does P1446 appear on Toyota or Lexus hybrids? A: No. P1446 as an IMA battery code is specific to Honda’s Civic Hybrid and Accord Hybrid platforms. Toyota and Lexus hybrid battery balance issues are reported through their own code series, primarily the P30xx block codes (P3011-P3027).
Q: My Honda Accord Hybrid shows P1446, is this the same fix as on a Civic Hybrid? A: The underlying condition is the same, IMA battery module voltage deviation, but the Honda Accord Hybrid IMA battery pack has a different physical configuration from the Civic Hybrid. Diagnostic and replacement procedures are model-specific. Call us with your VIN for a quote and diagnostic approach specific to your vehicle.
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