Engine
Poor Fuel Economy
Description
MPG drops noticeably compared to normal. Fill-ups happen more frequently than expected for the driving conditions.
Common Causes
Misfiring cylinders wasting fuel
Engine running rich (bad O2 sensor or MAF)
Stuck-open thermostat keeping engine cold
Degraded catalytic converter creating backpressure
Related Trouble Codes
P0101
Mass Air Flow Circuit Range/Performance
Moderate
P0128
Coolant Temperature Below Thermostat Regulating Temperature
Moderate
P0121
Throttle Position Sensor Range/Performance
Moderate
P0171
System Too Lean (Bank 1)
Moderate
P0172
System Too Rich (Bank 1)
Moderate
P0300
Random/Multiple Cylinder Misfire Detected
High
P0420
Catalyst System Efficiency Below Threshold (Bank 1)
Moderate
P0430
Catalyst System Efficiency Below Threshold (Bank 2)
Moderate
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Quick Info
| System | Engine |
| Related DTCs | 8 |