OBD Guide
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P3021

Battery Block 11 Becomes Weak

P3021 is an OBD-II diagnostic trouble code meaning: Battery Block 11 Becomes Weak. Common causes: battery cell wear, imbalance between battery cells. Estimated repair cost: $167–556.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$167–556 (est.)

Symptoms

  • Reduced engine power
  • Increased fuel consumption
  • Dashboard warning
  • Problems with regenerative braking
  • Reduced hybrid system efficiency

Causes

  • Battery cell wear
  • Imbalance between battery cells
  • Problems with the battery management system
  • Wiring harness damage
  • Contact corrosion

How to Fix

  1. Battery status diagnostics
  2. Checking cell balance
  3. Testing the Battery Management System
  4. Checking the integrity of the wiring harness
  5. Replace the battery pack if necessary

Related codes

P3020P3022P0A80

FAQ

What does the P3021 code mean?

P3021 is an OBD-II diagnostic trouble code that indicates: Battery Block 11 Becomes Weak

What causes a P3021 error code?

The most common causes of P3021 include: Battery cell wear; Imbalance between battery cells; Problems with the battery management system; Wiring harness damage.

How do I fix a P3021 diagnostic trouble code?

To fix P3021: Battery status diagnostics. Checking cell balance. Testing the Battery Management System. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P3021?

Yes, but get it checked soon

How much does it cost to fix P3021?

The estimated repair cost for P3021 is $167–556. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat