### P0420 Catalyst System Efficiency Below Threshold
– Typical Sources:
Faulty oxygen sensor [1]
– Recommended Fixes:
Diagnose fuel trim https://carautorepair.site/
### P0171 System Too Lean
– Possible Defects:
Faulty MAF sensor
– Testing Procedure:
Check fuel pressure [1][7]
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## Vehicle Service Vocabulary
### ABS (Anti-Lock Brake System)
– Function: Maintains steering control [7]
### Vehicle Computer System
– Responsibility: Controls ignition timing [7]
### Powertrain Elements
– Includes: Transmission [7]
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## Repair Process Steps
1. **Initial Diagnosis**:
Scan DTCs
2. **Part Evaluation**:
Check voltage
3. **Parts Replacement**:
Follow torque specs
4. **System Validation**:
Test drive vehicle
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## Necessary Equipment
| **Tool Type** | **Examples** | **Purpose** |
|—|—|—|
| Code Reader | Autel | Retrieve DTCs |
| Mechanical Tools | Torque wrench | Component repair |
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## Service Information References
### Auto Repair Source
– Capabilities:
TSB access [8]
OEM specifications
### Mobile Applications
– Auto Repair Documents:
ECU pinouts [5]
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## Budget Repair Strategies
– Routine checkups prevents major failures
– Understand DTC meanings to avoid unnecessary repairs
– Install quality alternatives when budget constrained [7]