OBD Guide
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P30B5

NOx Sensor 2 Signal Message Counter Incorrect

P30B5 is an OBD-II diagnostic trouble code meaning: NOx Sensor 2 Signal Message Counter Incorrect. Common causes: nox 2 sensor malfunction, damage to the wiring to the sensor. Estimated repair cost: $56–167.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$56–167 (est.)

Symptoms

  • Check Engine light comes on
  • Reduced engine power
  • Increased fuel consumption
  • The car goes into emergency mode
  • Unstable engine idling

Causes

  • NOx 2 sensor malfunction
  • Damage to the wiring to the sensor
  • Poor contact in the sensor connector
  • Problems with the engine control unit
  • Sensor contact corrosion

How to Fix

  1. Diagnose the NOx sensor using a scanner
  2. Check the integrity of wiring and connectors
  3. Clean the sensor contacts from corrosion
  4. If necessary, replace NOx 2 sensor
  5. Flash the control unit if necessary

Related codes

P30B4P30B6P2200

FAQ

What does the P30B5 code mean?

P30B5 is an OBD-II diagnostic trouble code that indicates: NOx Sensor 2 Signal Message Counter Incorrect

What causes a P30B5 error code?

The most common causes of P30B5 include: NOx 2 sensor malfunction; Damage to the wiring to the sensor; Poor contact in the sensor connector; Problems with the engine control unit.

How do I fix a P30B5 diagnostic trouble code?

To fix P30B5: Diagnose the NOx sensor using a scanner. Check the integrity of wiring and connectors. Clean the sensor contacts from corrosion. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P30B5?

Yes, but get it checked soon

How much does it cost to fix P30B5?

The estimated repair cost for P30B5 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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