OBD Guide

P21C6

Reductant Level Sensor B Stuck

P21C6 is an OBD-II diagnostic trouble code meaning: Reductant Level Sensor B Stuck. Common causes: level sensor float jammed, mechanical damage to the sensor. Estimated repair cost: $39–133.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$39–133 (est.)

Symptoms

  • Check Engine Light
  • Low AdBlue message on the dashboard
  • Engine power limitation
  • Incorrect reagent level readings
  • Inability to refill the AdBlue system

Causes

  • Level sensor float jammed
  • Mechanical damage to the sensor
  • Sensor contamination with urea crystals
  • Open or short circuit in the sensor circuit
  • Level sensor module malfunction

How to Fix

  1. Visual inspection of the level sensor for mechanical damage
  2. Cleaning the sensor and tank from crystallized urea
  3. Checking the sensor electrical circuit for opens and short circuits
  4. Replacing the reagent level sensor
  5. Resetting the error and testing the system

Related codes

Error P21C6 by Vehicle Brand

FAQ

What does the P21C6 code mean?

P21C6 is an OBD-II diagnostic trouble code that indicates: Reductant Level Sensor B Stuck

What causes a P21C6 error code?

The most common causes of P21C6 include: Level sensor float jammed; Mechanical damage to the sensor; Sensor contamination with urea crystals; Open or short circuit in the sensor circuit.

How do I fix a P21C6 diagnostic trouble code?

To fix P21C6: Visual inspection of the level sensor for mechanical damage. Cleaning the sensor and tank from crystallized urea. Checking the sensor electrical circuit for opens and short circuits. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P21C6?

Yes, but get it checked soon

How much does it cost to fix P21C6?

The estimated repair cost for P21C6 is $39–133. Actual cost depends on your vehicle, location, and labor rates.

See also: Russian version · NationStat