DEF Quality Sensor Circuit Malfunction (Generic)
The P4063 code means the vehicle's onboard diagnostic system has detected: DEF Quality Sensor Circuit Malfunction (Generic). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $150 - $500 (parts and labor)
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Common Symptoms
- Check Engine Light on
- DEF quality warning message
- SCR system may reduce operation
- Speed derate countdown possible
- DEF quality reading invalid
Probable Causes (Ranked by Likelihood)
- Failed DEF quality sensor Very High
- Contaminated DEF affecting sensor High
- Sensor connector corrosion from DEF exposure Moderate
- Wiring fault in DEF tank assembly Low
Step-by-Step Diagnostic Procedure
-
Check DEF quality with refractometer
-
Test DEF quality sensor output
-
Inspect sensor connector for DEF contamination
-
Verify DEF tank module wiring
Frequently Asked Questions
How do I check DEF quality?
Use a DEF refractometer, available for about $30. DEF should read 32.5% urea concentration.
Can bad DEF damage my truck?
Yes, contaminated DEF can damage the SCR catalyst, DEF injector, and DEF pump.
Can I drive with P4063?
You can drive short distances. If the DEF is bad, drain the tank and refill with fresh certified DEF.
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