DEF Level Sensor Circuit Malfunction (Generic)
The P4064 code means the vehicle's onboard diagnostic system has detected: DEF Level Sensor Circuit Malfunction (Generic). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $150 - $500 (parts and labor)
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Common Symptoms
- Check Engine Light on
- DEF level gauge inaccurate
- False low DEF warnings
- Speed derate may activate prematurely
- Unable to determine DEF quantity
Probable Causes (Ranked by Likelihood)
- Failed DEF level sensor in tank module Very High
- DEF crystallization on level sensor High
- Wiring fault in tank assembly Moderate
- PCM communication error Low
Step-by-Step Diagnostic Procedure
-
Check DEF level sensor output against actual level
-
Inspect tank module connector
-
Clean DEF level sensor if accessible
-
Test wiring between tank module and PCM
Frequently Asked Questions
Will I get stranded if the level sensor fails?
You will not run out of DEF unexpectedly. However, you may get false low-level warnings.
Can I drive with P4064?
You can drive short distances. Keep track of DEF usage manually.
Is the level sensor part of the tank module?
On most vehicles, the DEF level sensor, quality sensor, and temperature sensor are integrated into a single tank module.
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