SCR Catalyst Efficiency Below Threshold Bank 2 (Generic)
The P4073 code means the vehicle's onboard diagnostic system has detected: SCR Catalyst Efficiency Below Threshold Bank 2 (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
- Bank 2 NOx reduction insufficient
- Speed derate active
- DEF system fault
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Degraded bank 2 SCR catalyst Very High
- Contaminated catalyst from poor DEF High
- Bank 2 DEF injection fault Moderate
- Bank 2 NOx sensor inaccuracy Low
Step-by-Step Diagnostic Procedure
-
Compare bank 1 and bank 2 NOx reduction efficiency
-
Verify bank 2 DEF injection operation
-
Test bank 2 NOx sensors
-
Inspect bank 2 SCR for damage
Frequently Asked Questions
Why would only bank 2 fail?
Each bank has its own DEF injection and SCR catalyst. One side can fail independently.
Can I drive with P4073?
No, a speed derate countdown is active.
Should I replace both bank catalysts?
Verify the other bank is actually degraded before replacing both at $1500-4000 each.
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