SCR Catalyst Efficiency Below Threshold Bank 1 (Generic)
The P4072 code means the vehicle's onboard diagnostic system has detected: SCR Catalyst Efficiency Below Threshold Bank 1 (Generic). This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- hard
- Estimated cost
- $500 - $3000 (parts and labor)
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Common Symptoms
- Check Engine Light on
- NOx emissions too high
- Speed derate countdown active
- DEF warning light on
- Failed emissions inspection
Probable Causes (Ranked by Likelihood)
- Degraded SCR catalyst substrate Very High
- Contaminated SCR catalyst from bad DEF High
- DEF dosing system underdosing Moderate
- Incorrect NOx sensor readings Low
Step-by-Step Diagnostic Procedure
-
Check NOx reduction efficiency across SCR
-
Verify DEF quality and injection rate
-
Test NOx sensors for accuracy
-
Inspect SCR catalyst for physical damage
Frequently Asked Questions
Does P4072 always mean new SCR catalyst?
Not always. First verify the NOx sensors and DEF injection system are working properly.
Can I drive with P4072?
No, a derate countdown will be active. The vehicle will eventually be limited to 5 mph.
How much is an SCR catalyst?
An SCR catalyst replacement costs $1500-4000 depending on the vehicle.
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