OBD Guide
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P123D

Nitrogen Oxide Sensor Sensor Poisoning Binary Lambda Signal Too Rich

P123D is an OBD-II diagnostic trouble code meaning: Nitrogen Oxide Sensor Sensor Poisoning Binary Lambda Signal Too Rich. Common causes: nox sensor malfunction, nox sensor contamination. Estimated repair cost: $56–167.

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

Symptoms

  • Increased fuel consumption
  • Reduced engine power
  • Check Engine Light Is On
  • Increased exhaust smoke
  • Unstable engine idling

Causes

  • NOx sensor malfunction
  • NOx sensor contamination
  • Problems with fuel injectors
  • EGR system malfunction
  • Leaks in the fuel system

How to Fix

  1. Check the status of the NOx sensor
  2. Diagnose fuel injectors
  3. Check the operation of the EGR system
  4. Test the tightness of the fuel system
  5. Clean or replace NOx sensor if necessary

Related codes

P123CP123EP123F

FAQ

What does the P123D code mean?

P123D is an OBD-II diagnostic trouble code that indicates: Nitrogen Oxide Sensor Sensor Poisoning Binary Lambda Signal Too Rich

What causes a P123D error code?

The most common causes of P123D include: NOx sensor malfunction; NOx sensor contamination; Problems with fuel injectors; EGR system malfunction.

How do I fix a P123D diagnostic trouble code?

To fix P123D: Check the status of the NOx sensor. Diagnose fuel injectors. Check the operation of the EGR system. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P123D?

Yes, but get it checked soon

How much does it cost to fix P123D?

The estimated repair cost for P123D is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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