P21AC
Reductant Level Sensor B Circuit Intermittent/Erratic
P21AC is an OBD-II diagnostic trouble code meaning: Reductant Level Sensor B Circuit Intermittent/Erratic. Common causes: poor contact in the sensor connector, open or shorted wiring harness. Estimated repair cost: $28–89.
Symptoms
- Check Engine Light Is On
- Reduced engine power
- Low reagent message on instrument panel
- Unstable AdBlue level readings
- Possible transition to emergency mode
Causes
- Poor contact in the sensor connector
- Open or shorted wiring harness
- Reagent level sensor malfunction
- Problems with the SCR control unit
- Corrosion of contacts due to reagent ingress
How to Fix
- Check the connections and connectors of the sensor
- Test the sensor circuit for open and short circuits
- Check sensor resistance to specifications
- Replace the reagent level sensor if necessary
- Clear error codes and test drive
Related codes
Error P21AC by Vehicle Brand
FAQ
What does the P21AC code mean?
P21AC is an OBD-II diagnostic trouble code that indicates: Reductant Level Sensor B Circuit Intermittent/Erratic
What causes a P21AC error code?
The most common causes of P21AC include: Poor contact in the sensor connector; Open or shorted wiring harness; Reagent level sensor malfunction; Problems with the SCR control unit.
How do I fix a P21AC diagnostic trouble code?
To fix P21AC: Check the connections and connectors of the sensor. Test the sensor circuit for open and short circuits. Check sensor resistance to specifications. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with P21AC?
Limited driving only, diagnose soon
How much does it cost to fix P21AC?
The estimated repair cost for P21AC is $28–89. Actual cost depends on your vehicle, location, and labor rates.
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