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Question # 47
During testing, a car fails NOx limits but passes HC and CO. Scan tool shows functional O2 sensors and balanced trims. EGR valve opens when commanded, but backpressure readings indicate restricted passages. What is the cause?
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L1 Overview
| Name | Automotive Service Excellence Level 1 |
| Code | L1 |
| Vendor | Skilled Trades |
| Certification | ASE |
