### P0420 Catalyst System Efficiency Below Threshold
– Typical Sources:
Exhaust leaks [1]
– Suggested Repairs:
Diagnose fuel trim https://carautorepair.site/
### P0171 Air-Fuel Ratio Error
– Likely Problems:
Faulty MAF sensor
– Testing Procedure:
Inspect injectors [1][7]
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## Car Maintenance Terms
### Skid Prevention Technology
– Function: Maintains steering control [7]
### Engine Management Unit
– Role: Manages fuel injection [7]
### Drivetrain Components
– Includes: Differential [7]
—
## Service Procedure Stages
1. **Symptom Assessment**:
Scan DTCs
2. **System Verification**:
Test continuity
3. **Component Installation**:
Clear error codes
4. **System Validation**:
Confirm warning light reset
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## Critical Instruments
| **Tool Type** | **Examples** | **Purpose** |
|—|—|—|
| Code Reader | BlueDriver | Retrieve DTCs |
| Hand Instruments | Torque wrench | Electrical testing |
—
## Repair Documentation Sources
### Auto Repair Source
– Features:
TSB access [8]
Factory repair procedures
### Mobile Applications
– Auto Repair Documents:
Component testing guides [5]
—
## Affordable Maintenance Advice
– Preventative service prevents major failures
– Understand DTC meanings to avoid unnecessary repairs
– Select certified components when OEM prices prohibitive [7]