### P0420 Catalyst System Efficiency Below Threshold
– Frequent Reasons:
Worn catalytic converter [1]
– Recommended Fixes:
Diagnose fuel trim https://carautorepair.site/
### P0171 Air-Fuel Ratio Error
– Likely Problems:
Vacuum leaks
– Diagnostic Steps:
Smoke test intake [1][7]
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## Car Maintenance Terms
### ABS (Anti-Lock Brake System)
– Function: Maintains steering control [7]
### Vehicle Computer System
– Role: Controls ignition timing [7]
### Powertrain Elements
– Contains: Transmission [7]
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## Mechanical Fixing Workflow
1. **Symptom Assessment**:
Scan DTCs
2. **System Verification**:
Test continuity
3. **Defective Unit Swap**:
Use OEM parts
4. **Final Quality Check**:
Confirm warning light reset
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## Necessary Equipment
| **Tool Type** | **Examples** | **Purpose** |
|—|—|—|
| OBD-II Tool | Autel | Retrieve DTCs |
| Hand Instruments | Torque wrench | Electrical testing |
—
## Technical Data Resources
### Auto Repair Source
– Capabilities:
Component locations [8]
Factory repair procedures
### Smartphone Tools
– Auto Repair Documents:
Electrical diagrams [5]
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## Cost-Saving Tips
– Preventative service avoids costly repairs
– Learn basic diagnostics to avoid unnecessary repairs
– Select certified components when OEM prices prohibitive [7]