P21AF — Reductant Level Sensor C Circuit Low

What Does P21AF Mean?

P21AF is a diagnostic trouble code indicating: Reductant Level Sensor C Circuit Low. This code relates to the powertrain system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of P21AF

⚠️ Check Engine Light (MIL) illuminated
⚠️ Reductant Level Sensor C reading at zero or minimum value
⚠️ Related system not functioning or in fail-safe mode
⚠️ Reduced engine performance

Common Causes

🔍 Open or broken wire in Reductant Level Sensor C circuit
🔍 Poor ground connection at Reductant Level Sensor C
🔍 Faulty Reductant Level Sensor C with no output signal
🔍 Disconnected or loose Reductant Level Sensor C connector
🔍 Blown fuse in related circuit

Frequently Asked Questions

What does P21AF mean?

P21AF indicates: Reductant Level Sensor C Circuit Low. The vehicle's computer has detected that the Reductant Level Sensor C is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P21AF?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P21AF for extended periods may cause additional problems.

How much does it cost to fix P21AF?

Repair costs for P21AF typically range from $20 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Repair broken wire or restore ground in Reductant Level Sensor C circuit
🔧 Clean and secure Reductant Level Sensor C connector and ground points
🔧 Replace failed Reductant Level Sensor C

1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

P21AF: Reductant Level Sensor C Circuit Low